Los métodos getter y setter se utilizan con frecuencia en la programación Java. Métodos getter y setter en Java se utilizan ampliamente para acceder y manipular los valores de los campos de clase. Normalmente, los campos de clase están decorados con un especificador de acceso privado. Así, para acceder a ellos se utilizan especificadores de acceso público con los métodos getter y setter.
La necesidad del método Getter y Setter
Se puede argumentar que se declaran los campos de clase como públicos y se eliminan los métodos getter y setter. Sin embargo, ese estilo de codificación es malo y se puede poner algún valor absurdo en los campos de clase. Entendámoslo con la ayuda de un ejemplo.
public class GetterSetterExample { public salary; public storeSalaryDB(int salary) { // code for storing the salary in the database } // main method public static void main(String argvs[]) { GetterSetterExample obj = new GetterSetterExample(); obj.salary = -50000; // storing salary in database obj.storeSalaryDB(salary); } } Observe que el código está almacenando un salario negativo en la base de datos que es incorrecto. Una organización nunca acredita un salario negativo a la cuenta de un empleado. Asignar una cantidad absurda a la variable salario ocurrió porque está declarada con un especificador de acceso público. La forma correcta de escribir el código anterior es:
public class GetterSetterExample { private salary; // a setter method that assign a // value to the salary variable void setSalary(int s) { if(s <0 ) { s="-s;" } this.salary="s;" a getter mehtod to retrieve the salary int getsalary() return this.salary; public storesalarydb(int salary) code for storing in database system.out.println('the ') main method static void main(string argvs[]) creating an object of class gettersetterexample obj="new" gettersetterexample(); obj.setsalary(-50000); obj.storesalarydb(salary); < pre> <p>Now, we can see better control over what we send to the database to store. Whenever the salary is negative, we are converting the salary into a positive value, and then we are sending it to the database to store. Thus, no matter what value we send to the setter method, the if-block of the setter method takes care of the absurd value and thus gives better control on the salary value.</p> <h2>Getter Setter Java Program</h2> <p> <strong>FileName:</strong> GetterSetterExample1.java</p> <pre> class Employee { // class member variable private int eId; private String eName; private String eDesignation; private String eCompany; public int getEmpId() { return eId; } public void setEmpId(final int eId) { this.eId = eId; } public String getEmpName() { return eName; } public void setEmpName(final String eName) { // Validating the employee's name and // throwing an exception if the name is null or its length is less than or equal to 0. if(eName == null || eName.length() <= 0) { throw new illegalargumentexception(); } this.ename="eName;" public string getempdesignation() return edesignation; void setempdesignation(final edesignation) this.edesignation="eDesignation;" getempcompany() ecompany; setempcompany(final ecompany) this.ecompany="eCompany;" for printing the values @override tostring() str="Employee: [id = " + getempid() ', name=" + getEmpName() + " , designation=" + getEmpDesignation() + " company=" + getEmpCompany() + " ]'; str; main class. class gettersetterexample1 method static main(string argvs[]) creating an object of employee final emp="new" employee(); details are getting set using setter methods. emp.setempid(107); emp.setempname('kathy'); emp.setempdesignation('software tester'); emp.setempcompany('xyz corporation'); displaying 'tostring()' method, which uses getter methods system.out.println(emp.tostring()); < pre> <p> <strong>Output:</strong> </p> <pre> Employee: [id = 107, name = Kathy, designation = Software Tester, company = XYZ Corporation] </pre> <h2>Bad Practices in Getter and Setter Methods</h2> <p>There are some common bad practices that people usually do when they deal with the getter and setter methods.</p> <h3>Bad Practice 1:</h3> <p>Using getter and setter for the variable that is declared with low restricted scope.</p> <pre> public salary; void setSalary(int s) { salary = s; } int getSalary() { return salary; } </pre> <p>It is evident that from the main method, one can directly access the variable salary, which is not only bad but also makes the presence of the getter and setter methods irrelevant.</p> <h3>Bad Practice 2:</h3> <p>Using an object reference in the setter method. Consider the following program.</p> <p> <strong>FileName:</strong> GetterSetterExample2.java</p> <pre> class ABC { private int[] val; void setVal(int[] arr) { this.val = arr; // line 7 } // for displaying the value // present in the val array void display() { int size = (this.val).length; for(int i = 0; i <size; i++) { system.out.print(this.val[i] + ' '); } main class public gettersetterexample2 method static void main(string argvs[]) instantiating the abc obj="new" abc(); int mainarr[]="{3," 4, 6, 8, 78, 9}; invoking setter obj.setval(mainarr); display obj.display(); updating value at 0th index mainarr[0]="-1;" system.out.println(); < pre> <p> <strong>Output:</strong> </p> <pre> 3 4 6 8 78 9 -1 4 6 8 78 9 </pre> <p> <strong>Explanation:</strong> </p> <p>References are a bit tricky to deal with! In the above code, at line 43, the value got updated at the 0th index for array mainArr[]. However, it also got reflected in the array val[]. It should not happen as val[] array is declared private; hence, it is expected that any code outside of the class ABC should not modify it. However, because of the references, everything is messed up. The setter method setVal() expecting a reference of an int array, and at line 7, the reference of the int arr[] is getting copied to val[]. Note that the reference variable arr[] is storing the reference of the array mainArr[]. Thus, we can say val[] is storing the reference of the mainArr[].</p> <p>Therefore, whatever we change in the mainArr[] also gets reflected in the val[] array, which violates the purpose of the setter method. Also, there is no meaning in adding the private access specifier to the val[] array; because one can change the value of the val[] array in the main method, which is evident by looking at the output.</p> <p>A better way of writing the above code is:</p> <p> <strong>FileName:</strong> GetterSetterExample3.java</p> <pre> class ABC { private int[] val; void setVal(int[] arr) { int size = arr.length; // allocating the memory as // per the array arr size val = new int[size]; // line 11 for(int i = 0; i <size; 17 53 i++) { copying the value one by into val array this.val[i]="arr[i];" line } for displaying present in void display() int size="(this.val).length;" for(int i="0;" < size; system.out.print(this.val[i] + ' '); main class. public class gettersetterexample3 method static main(string argvs[]) instantiating abc obj="new" abc(); mainarr[]="{3," 4, 6, 8, 78, 9}; invoking setter obj.setval(mainarr); display obj.display(); updating at 0th index mainarr[0]="-1;" system.out.println(); again pre> <p> <strong>Output:</strong> </p> <pre> 3 4 6 8 78 9 3 4 6 8 78 9 </pre> <p> <strong>Explanation:</strong> </p> <p>In the above code, we are doing the deep copy of elements of the array arr[]. In line 11, we are creating an entirely new array. Thus, the val[] is not referring to the arr[]. Also, in line 17, only values of the element are getting copied. Therefore, when we change the value of the 0th element at line 53, the change is not reflected in the val[]. Thus, the above code respects the encapsulation of the private member variable val[].</p> <h3>Bad Practice 3:</h3> <p>Returning an object reference in the getter method. Observe the following program.</p> <p> <strong>FileName:</strong> GetterSetterExample4.java</p> <pre> class ABC { private int[] val = {67, 43, 68, 112, 70, 12}; // the getter method public int[] getVal() { // returning the reference return val; // line 9 } // for displaying the value // present in the val array void display() { int size = (this.val).length; for(int i = 0; i <size; 42 i++) { system.out.print(this.val[i] + ' '); } main class. public class gettersetterexample4 method static void main(string argvs[]) instantiating the abc obj="new" abc(); invoking getter and storing result int arr[]="obj.getVal();" display obj.display(); updating value at 0th index arr[0]="-1;" line system.out.println(); again < pre> <p> <strong>Output:</strong> </p> <pre> 67 43 68 112 70 12 -1 43 68 112 70 12 </pre> <p> <strong>Explanation:</strong> </p> <p>The above code is not handling the references properly. The getter method is returning the reference of the array. The arr[] is storing the reference of the array val[], which is declared private in the class ABC. Because of exposing the reference to the outer world, arr[] can manipulate the val[], and thus, the encapsulation of the class ABC is breached. The proper way to handle the above is:</p> <p> <strong>FileName:</strong> GetterSetterExample5.java</p> <pre> class ABC { private int[] val = {67, 43, 68, 112, 70, 12}; // the getter method public int[] getVal() { int size = val.length; // creating a new array int temp[] = new int[size]; // copying the content of the array to temp array for(int i = 0; i <size; 54 i++) { temp[i]="val[i];" } return temp; for displaying the value present in val array void display() int size="(this.val).length;" for(int i="0;" < size; system.out.print(this.val[i] + ' '); main class. public class gettersetterexample5 method static main(string argvs[]) instantiating abc obj="new" abc(); invoking getter and storing result arr[]="obj.getVal();" display obj.display(); updating at 0th index arr[0]="-1;" line system.out.println(); pre> <p> <strong>Output:</strong> </p> <pre> 67 43 68 112 70 12 67 43 68 112 70 12 </pre> <p> <strong>Explanation:</strong> In the above code, the reference of the private array is not sent to the outside world. In the getter method, a new array is created whose reference is sent to the main method. Therefore, when the value at the 0th index gets changed at line 54, that change impacts the temp[] array, not the private array val[]. Thus, the encapsulation of the class ABC is maintained, as the reference of the array val[] is not exposed to the outside world.</p> <h4>Note 1: For primitive data types (int, char, etc.), one does not need to create a copy in the getter and setter methods, as the concept of references is absent for the primitive data types.</h4> <h4>Note 2: Strings object types also work on the references. However, unlike the above examples, one does not need to take care of the String references exposed to the outside world. It is because Strings are immutable. Thus, when one manipulates the string in the main method (or anywhere else), a new String object is created, and the previous one remains untouched.</h4> <p> <strong>FileName:</strong> GetterSetterExample6.java</p> <pre> class ABC { private String str = null; // a setter method void setVal(String s) { // reference is getting copied this.str = s; } // for displaying the string void display() { System.out.println( 'The String is: ' + this.str); } } // Main class. public class GetterSetterExample6 { // main method public static void main(String argvs[]) { // creating an object of the class ABC ABC obj = new ABC(); // input string String inputStr = 'Hello India!'; // invoking the setter method obj.setVal(inputStr); obj.display(); // manipulation is not allowed! // it leads to the creation of the new string inputStr = 'Hello World!'; obj.display(); } } </pre> <p> <strong>Output:</strong> </p> <pre> The String is: Hello India! The String is: Hello India! </pre> <hr></size;></pre></size;></pre></size;></pre></size;></pre></=></pre></0> Malas prácticas en los métodos Getter y Setter
Hay algunas malas prácticas comunes que la gente suele realizar cuando trabaja con los métodos getter y setter.
ordenamiento por selección en java
Mala práctica 1:
Usar getter y setter para la variable que se declara con un alcance restringido bajo.
public salary; void setSalary(int s) { salary = s; } int getSalary() { return salary; } Es evidente que desde el método principal se puede acceder directamente al salario variable, lo cual no sólo es malo sino que además hace irrelevante la presencia de los métodos getter y setter.
Mala práctica 2:
Usar una referencia de objeto en el método de establecimiento. Considere el siguiente programa.
Nombre del archivo: GetterSetterExample2.java
class ABC { private int[] val; void setVal(int[] arr) { this.val = arr; // line 7 } // for displaying the value // present in the val array void display() { int size = (this.val).length; for(int i = 0; i <size; i++) { system.out.print(this.val[i] + \' \'); } main class public gettersetterexample2 method static void main(string argvs[]) instantiating the abc obj="new" abc(); int mainarr[]="{3," 4, 6, 8, 78, 9}; invoking setter obj.setval(mainarr); display obj.display(); updating value at 0th index mainarr[0]="-1;" system.out.println(); < pre> <p> <strong>Output:</strong> </p> <pre> 3 4 6 8 78 9 -1 4 6 8 78 9 </pre> <p> <strong>Explanation:</strong> </p> <p>References are a bit tricky to deal with! In the above code, at line 43, the value got updated at the 0th index for array mainArr[]. However, it also got reflected in the array val[]. It should not happen as val[] array is declared private; hence, it is expected that any code outside of the class ABC should not modify it. However, because of the references, everything is messed up. The setter method setVal() expecting a reference of an int array, and at line 7, the reference of the int arr[] is getting copied to val[]. Note that the reference variable arr[] is storing the reference of the array mainArr[]. Thus, we can say val[] is storing the reference of the mainArr[].</p> <p>Therefore, whatever we change in the mainArr[] also gets reflected in the val[] array, which violates the purpose of the setter method. Also, there is no meaning in adding the private access specifier to the val[] array; because one can change the value of the val[] array in the main method, which is evident by looking at the output.</p> <p>A better way of writing the above code is:</p> <p> <strong>FileName:</strong> GetterSetterExample3.java</p> <pre> class ABC { private int[] val; void setVal(int[] arr) { int size = arr.length; // allocating the memory as // per the array arr size val = new int[size]; // line 11 for(int i = 0; i <size; 17 53 i++) { copying the value one by into val array this.val[i]="arr[i];" line } for displaying present in void display() int size="(this.val).length;" for(int i="0;" < size; system.out.print(this.val[i] + \' \'); main class. public class gettersetterexample3 method static main(string argvs[]) instantiating abc obj="new" abc(); mainarr[]="{3," 4, 6, 8, 78, 9}; invoking setter obj.setval(mainarr); display obj.display(); updating at 0th index mainarr[0]="-1;" system.out.println(); again pre> <p> <strong>Output:</strong> </p> <pre> 3 4 6 8 78 9 3 4 6 8 78 9 </pre> <p> <strong>Explanation:</strong> </p> <p>In the above code, we are doing the deep copy of elements of the array arr[]. In line 11, we are creating an entirely new array. Thus, the val[] is not referring to the arr[]. Also, in line 17, only values of the element are getting copied. Therefore, when we change the value of the 0th element at line 53, the change is not reflected in the val[]. Thus, the above code respects the encapsulation of the private member variable val[].</p> <h3>Bad Practice 3:</h3> <p>Returning an object reference in the getter method. Observe the following program.</p> <p> <strong>FileName:</strong> GetterSetterExample4.java</p> <pre> class ABC { private int[] val = {67, 43, 68, 112, 70, 12}; // the getter method public int[] getVal() { // returning the reference return val; // line 9 } // for displaying the value // present in the val array void display() { int size = (this.val).length; for(int i = 0; i <size; 42 i++) { system.out.print(this.val[i] + \' \'); } main class. public class gettersetterexample4 method static void main(string argvs[]) instantiating the abc obj="new" abc(); invoking getter and storing result int arr[]="obj.getVal();" display obj.display(); updating value at 0th index arr[0]="-1;" line system.out.println(); again < pre> <p> <strong>Output:</strong> </p> <pre> 67 43 68 112 70 12 -1 43 68 112 70 12 </pre> <p> <strong>Explanation:</strong> </p> <p>The above code is not handling the references properly. The getter method is returning the reference of the array. The arr[] is storing the reference of the array val[], which is declared private in the class ABC. Because of exposing the reference to the outer world, arr[] can manipulate the val[], and thus, the encapsulation of the class ABC is breached. The proper way to handle the above is:</p> <p> <strong>FileName:</strong> GetterSetterExample5.java</p> <pre> class ABC { private int[] val = {67, 43, 68, 112, 70, 12}; // the getter method public int[] getVal() { int size = val.length; // creating a new array int temp[] = new int[size]; // copying the content of the array to temp array for(int i = 0; i <size; 54 i++) { temp[i]="val[i];" } return temp; for displaying the value present in val array void display() int size="(this.val).length;" for(int i="0;" < size; system.out.print(this.val[i] + \' \'); main class. public class gettersetterexample5 method static main(string argvs[]) instantiating abc obj="new" abc(); invoking getter and storing result arr[]="obj.getVal();" display obj.display(); updating at 0th index arr[0]="-1;" line system.out.println(); pre> <p> <strong>Output:</strong> </p> <pre> 67 43 68 112 70 12 67 43 68 112 70 12 </pre> <p> <strong>Explanation:</strong> In the above code, the reference of the private array is not sent to the outside world. In the getter method, a new array is created whose reference is sent to the main method. Therefore, when the value at the 0th index gets changed at line 54, that change impacts the temp[] array, not the private array val[]. Thus, the encapsulation of the class ABC is maintained, as the reference of the array val[] is not exposed to the outside world.</p> <h4>Note 1: For primitive data types (int, char, etc.), one does not need to create a copy in the getter and setter methods, as the concept of references is absent for the primitive data types.</h4> <h4>Note 2: Strings object types also work on the references. However, unlike the above examples, one does not need to take care of the String references exposed to the outside world. It is because Strings are immutable. Thus, when one manipulates the string in the main method (or anywhere else), a new String object is created, and the previous one remains untouched.</h4> <p> <strong>FileName:</strong> GetterSetterExample6.java</p> <pre> class ABC { private String str = null; // a setter method void setVal(String s) { // reference is getting copied this.str = s; } // for displaying the string void display() { System.out.println( 'The String is: ' + this.str); } } // Main class. public class GetterSetterExample6 { // main method public static void main(String argvs[]) { // creating an object of the class ABC ABC obj = new ABC(); // input string String inputStr = 'Hello India!'; // invoking the setter method obj.setVal(inputStr); obj.display(); // manipulation is not allowed! // it leads to the creation of the new string inputStr = 'Hello World!'; obj.display(); } } </pre> <p> <strong>Output:</strong> </p> <pre> The String is: Hello India! The String is: Hello India! </pre> <hr></size;></pre></size;></pre></size;></pre></size;> Explicación:
¡Las referencias son un poco difíciles de manejar! En el código anterior, en la línea 43, el valor se actualizó en el índice 0 de la matriz mainArr[]. Sin embargo, también se reflejó en la matriz val[]. No debería suceder ya que la matriz val[] se declara privada; por lo tanto, se espera que cualquier código fuera de la clase ABC no la modifique. Sin embargo, debido a las referencias, todo está desordenado. El método de establecimiento setVal() espera una referencia de una matriz int, y en la línea 7, la referencia de int arr[] se copia a val[]. Tenga en cuenta que la variable de referencia arr[] almacena la referencia de la matriz mainArr[]. Por lo tanto, podemos decir que val[] está almacenando la referencia de mainArr[].
contiene pitón
Por lo tanto, cualquier cambio que cambiemos en mainArr[] también se refleja en la matriz val[], lo que viola el propósito del método setter. Además, no tiene sentido agregar el especificador de acceso privado a la matriz val[]; porque se puede cambiar el valor de la matriz val[] en el método principal, lo cual es evidente al observar la salida.
Una mejor manera de escribir el código anterior es:
Nombre del archivo: GetterSetterExample3.java
class ABC { private int[] val; void setVal(int[] arr) { int size = arr.length; // allocating the memory as // per the array arr size val = new int[size]; // line 11 for(int i = 0; i <size; 17 53 i++) { copying the value one by into val array this.val[i]="arr[i];" line } for displaying present in void display() int size="(this.val).length;" for(int i="0;" < size; system.out.print(this.val[i] + \' \'); main class. public class gettersetterexample3 method static main(string argvs[]) instantiating abc obj="new" abc(); mainarr[]="{3," 4, 6, 8, 78, 9}; invoking setter obj.setval(mainarr); display obj.display(); updating at 0th index mainarr[0]="-1;" system.out.println(); again pre> <p> <strong>Output:</strong> </p> <pre> 3 4 6 8 78 9 3 4 6 8 78 9 </pre> <p> <strong>Explanation:</strong> </p> <p>In the above code, we are doing the deep copy of elements of the array arr[]. In line 11, we are creating an entirely new array. Thus, the val[] is not referring to the arr[]. Also, in line 17, only values of the element are getting copied. Therefore, when we change the value of the 0th element at line 53, the change is not reflected in the val[]. Thus, the above code respects the encapsulation of the private member variable val[].</p> <h3>Bad Practice 3:</h3> <p>Returning an object reference in the getter method. Observe the following program.</p> <p> <strong>FileName:</strong> GetterSetterExample4.java</p> <pre> class ABC { private int[] val = {67, 43, 68, 112, 70, 12}; // the getter method public int[] getVal() { // returning the reference return val; // line 9 } // for displaying the value // present in the val array void display() { int size = (this.val).length; for(int i = 0; i <size; 42 i++) { system.out.print(this.val[i] + \' \'); } main class. public class gettersetterexample4 method static void main(string argvs[]) instantiating the abc obj="new" abc(); invoking getter and storing result int arr[]="obj.getVal();" display obj.display(); updating value at 0th index arr[0]="-1;" line system.out.println(); again < pre> <p> <strong>Output:</strong> </p> <pre> 67 43 68 112 70 12 -1 43 68 112 70 12 </pre> <p> <strong>Explanation:</strong> </p> <p>The above code is not handling the references properly. The getter method is returning the reference of the array. The arr[] is storing the reference of the array val[], which is declared private in the class ABC. Because of exposing the reference to the outer world, arr[] can manipulate the val[], and thus, the encapsulation of the class ABC is breached. The proper way to handle the above is:</p> <p> <strong>FileName:</strong> GetterSetterExample5.java</p> <pre> class ABC { private int[] val = {67, 43, 68, 112, 70, 12}; // the getter method public int[] getVal() { int size = val.length; // creating a new array int temp[] = new int[size]; // copying the content of the array to temp array for(int i = 0; i <size; 54 i++) { temp[i]="val[i];" } return temp; for displaying the value present in val array void display() int size="(this.val).length;" for(int i="0;" < size; system.out.print(this.val[i] + \' \'); main class. public class gettersetterexample5 method static main(string argvs[]) instantiating abc obj="new" abc(); invoking getter and storing result arr[]="obj.getVal();" display obj.display(); updating at 0th index arr[0]="-1;" line system.out.println(); pre> <p> <strong>Output:</strong> </p> <pre> 67 43 68 112 70 12 67 43 68 112 70 12 </pre> <p> <strong>Explanation:</strong> In the above code, the reference of the private array is not sent to the outside world. In the getter method, a new array is created whose reference is sent to the main method. Therefore, when the value at the 0th index gets changed at line 54, that change impacts the temp[] array, not the private array val[]. Thus, the encapsulation of the class ABC is maintained, as the reference of the array val[] is not exposed to the outside world.</p> <h4>Note 1: For primitive data types (int, char, etc.), one does not need to create a copy in the getter and setter methods, as the concept of references is absent for the primitive data types.</h4> <h4>Note 2: Strings object types also work on the references. However, unlike the above examples, one does not need to take care of the String references exposed to the outside world. It is because Strings are immutable. Thus, when one manipulates the string in the main method (or anywhere else), a new String object is created, and the previous one remains untouched.</h4> <p> <strong>FileName:</strong> GetterSetterExample6.java</p> <pre> class ABC { private String str = null; // a setter method void setVal(String s) { // reference is getting copied this.str = s; } // for displaying the string void display() { System.out.println( 'The String is: ' + this.str); } } // Main class. public class GetterSetterExample6 { // main method public static void main(String argvs[]) { // creating an object of the class ABC ABC obj = new ABC(); // input string String inputStr = 'Hello India!'; // invoking the setter method obj.setVal(inputStr); obj.display(); // manipulation is not allowed! // it leads to the creation of the new string inputStr = 'Hello World!'; obj.display(); } } </pre> <p> <strong>Output:</strong> </p> <pre> The String is: Hello India! The String is: Hello India! </pre> <hr></size;></pre></size;></pre></size;> Explicación:
En el código anterior, estamos haciendo una copia profunda de los elementos de la matriz arr[]. En la línea 11, estamos creando una matriz completamente nueva. Por lo tanto, val[] no se refiere a arr[]. Además, en la línea 17, solo se copian los valores del elemento. Por lo tanto, cuando cambiamos el valor del elemento 0 en la línea 53, el cambio no se refleja en val[]. Por tanto, el código anterior respeta la encapsulación de la variable miembro privada val[].
aplicaciones de computación en la nube
Mala práctica 3:
Devolver una referencia de objeto en el método getter. Observe el siguiente programa.
cuantas semanas hay en un mes
Nombre del archivo: GetterSetterExample4.java
class ABC { private int[] val = {67, 43, 68, 112, 70, 12}; // the getter method public int[] getVal() { // returning the reference return val; // line 9 } // for displaying the value // present in the val array void display() { int size = (this.val).length; for(int i = 0; i <size; 42 i++) { system.out.print(this.val[i] + \' \'); } main class. public class gettersetterexample4 method static void main(string argvs[]) instantiating the abc obj="new" abc(); invoking getter and storing result int arr[]="obj.getVal();" display obj.display(); updating value at 0th index arr[0]="-1;" line system.out.println(); again < pre> <p> <strong>Output:</strong> </p> <pre> 67 43 68 112 70 12 -1 43 68 112 70 12 </pre> <p> <strong>Explanation:</strong> </p> <p>The above code is not handling the references properly. The getter method is returning the reference of the array. The arr[] is storing the reference of the array val[], which is declared private in the class ABC. Because of exposing the reference to the outer world, arr[] can manipulate the val[], and thus, the encapsulation of the class ABC is breached. The proper way to handle the above is:</p> <p> <strong>FileName:</strong> GetterSetterExample5.java</p> <pre> class ABC { private int[] val = {67, 43, 68, 112, 70, 12}; // the getter method public int[] getVal() { int size = val.length; // creating a new array int temp[] = new int[size]; // copying the content of the array to temp array for(int i = 0; i <size; 54 i++) { temp[i]="val[i];" } return temp; for displaying the value present in val array void display() int size="(this.val).length;" for(int i="0;" < size; system.out.print(this.val[i] + \' \'); main class. public class gettersetterexample5 method static main(string argvs[]) instantiating abc obj="new" abc(); invoking getter and storing result arr[]="obj.getVal();" display obj.display(); updating at 0th index arr[0]="-1;" line system.out.println(); pre> <p> <strong>Output:</strong> </p> <pre> 67 43 68 112 70 12 67 43 68 112 70 12 </pre> <p> <strong>Explanation:</strong> In the above code, the reference of the private array is not sent to the outside world. In the getter method, a new array is created whose reference is sent to the main method. Therefore, when the value at the 0th index gets changed at line 54, that change impacts the temp[] array, not the private array val[]. Thus, the encapsulation of the class ABC is maintained, as the reference of the array val[] is not exposed to the outside world.</p> <h4>Note 1: For primitive data types (int, char, etc.), one does not need to create a copy in the getter and setter methods, as the concept of references is absent for the primitive data types.</h4> <h4>Note 2: Strings object types also work on the references. However, unlike the above examples, one does not need to take care of the String references exposed to the outside world. It is because Strings are immutable. Thus, when one manipulates the string in the main method (or anywhere else), a new String object is created, and the previous one remains untouched.</h4> <p> <strong>FileName:</strong> GetterSetterExample6.java</p> <pre> class ABC { private String str = null; // a setter method void setVal(String s) { // reference is getting copied this.str = s; } // for displaying the string void display() { System.out.println( 'The String is: ' + this.str); } } // Main class. public class GetterSetterExample6 { // main method public static void main(String argvs[]) { // creating an object of the class ABC ABC obj = new ABC(); // input string String inputStr = 'Hello India!'; // invoking the setter method obj.setVal(inputStr); obj.display(); // manipulation is not allowed! // it leads to the creation of the new string inputStr = 'Hello World!'; obj.display(); } } </pre> <p> <strong>Output:</strong> </p> <pre> The String is: Hello India! The String is: Hello India! </pre> <hr></size;></pre></size;> Explicación:
El código anterior no maneja las referencias correctamente. El método getter devuelve la referencia de la matriz. Arr[] almacena la referencia de la matriz val[], que se declara privada en la clase ABC. Debido a que se expone la referencia al mundo exterior, arr[] puede manipular val[] y, por lo tanto, se viola la encapsulación de la clase ABC. La forma correcta de manejar lo anterior es:
Nombre del archivo: GetterSetterExample5.java
class ABC { private int[] val = {67, 43, 68, 112, 70, 12}; // the getter method public int[] getVal() { int size = val.length; // creating a new array int temp[] = new int[size]; // copying the content of the array to temp array for(int i = 0; i <size; 54 i++) { temp[i]="val[i];" } return temp; for displaying the value present in val array void display() int size="(this.val).length;" for(int i="0;" < size; system.out.print(this.val[i] + \\' \\'); main class. public class gettersetterexample5 method static main(string argvs[]) instantiating abc obj="new" abc(); invoking getter and storing result arr[]="obj.getVal();" display obj.display(); updating at 0th index arr[0]="-1;" line system.out.println(); pre> <p> <strong>Output:</strong> </p> <pre> 67 43 68 112 70 12 67 43 68 112 70 12 </pre> <p> <strong>Explanation:</strong> In the above code, the reference of the private array is not sent to the outside world. In the getter method, a new array is created whose reference is sent to the main method. Therefore, when the value at the 0th index gets changed at line 54, that change impacts the temp[] array, not the private array val[]. Thus, the encapsulation of the class ABC is maintained, as the reference of the array val[] is not exposed to the outside world.</p> <h4>Note 1: For primitive data types (int, char, etc.), one does not need to create a copy in the getter and setter methods, as the concept of references is absent for the primitive data types.</h4> <h4>Note 2: Strings object types also work on the references. However, unlike the above examples, one does not need to take care of the String references exposed to the outside world. It is because Strings are immutable. Thus, when one manipulates the string in the main method (or anywhere else), a new String object is created, and the previous one remains untouched.</h4> <p> <strong>FileName:</strong> GetterSetterExample6.java</p> <pre> class ABC { private String str = null; // a setter method void setVal(String s) { // reference is getting copied this.str = s; } // for displaying the string void display() { System.out.println( 'The String is: ' + this.str); } } // Main class. public class GetterSetterExample6 { // main method public static void main(String argvs[]) { // creating an object of the class ABC ABC obj = new ABC(); // input string String inputStr = 'Hello India!'; // invoking the setter method obj.setVal(inputStr); obj.display(); // manipulation is not allowed! // it leads to the creation of the new string inputStr = 'Hello World!'; obj.display(); } } </pre> <p> <strong>Output:</strong> </p> <pre> The String is: Hello India! The String is: Hello India! </pre> <hr></size;> Explicación: En el código anterior, la referencia de la matriz privada no se envía al mundo exterior. En el método getter se crea una nueva matriz cuya referencia se envía al método principal. Por lo tanto, cuando el valor en el índice 0 se cambia en la línea 54, ese cambio afecta la matriz temp[], no la matriz privada val[]. Así, se mantiene la encapsulación de la clase ABC, ya que la referencia del array val[] no está expuesta al mundo exterior.
Nota 1: Para los tipos de datos primitivos (int, char, etc.), no es necesario crear una copia en los métodos getter y setter, ya que el concepto de referencias está ausente para los tipos de datos primitivos.
Nota 2: Los tipos de objetos de cadena también funcionan en las referencias. Sin embargo, a diferencia de los ejemplos anteriores, no es necesario cuidar las referencias de cadenas expuestas al mundo exterior. Es porque las cadenas son inmutables. Por lo tanto, cuando uno manipula la cadena en el método principal (o en cualquier otro lugar), se crea un nuevo objeto String y el anterior permanece intacto.
Nombre del archivo: GetterSetterExample6.java
class ABC { private String str = null; // a setter method void setVal(String s) { // reference is getting copied this.str = s; } // for displaying the string void display() { System.out.println( 'The String is: ' + this.str); } } // Main class. public class GetterSetterExample6 { // main method public static void main(String argvs[]) { // creating an object of the class ABC ABC obj = new ABC(); // input string String inputStr = 'Hello India!'; // invoking the setter method obj.setVal(inputStr); obj.display(); // manipulation is not allowed! // it leads to the creation of the new string inputStr = 'Hello World!'; obj.display(); } } Producción:
The String is: Hello India! The String is: Hello India!