Accessing Private Members of a Class

Posted on 05/07/2012 by Admin

Normally You cannot access the private variables and methods of a Class,from outside of the class.
By Reflection API,gives us the facility to access them
The following program demonstrates the same

Demo.java

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public class Demo {     private String msg= "Satya";     private String show() {         System.out.println("show()::You cannot access me from outside");         return "Java";     } }

AccessingPrivateVariable .java

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import java.lang.reflect.Field; import java.lang.reflect.InvocationTargetException; import java.lang.reflect.Method; public class AccessingPrivateVariable {     public static void main(String[] args)throws IllegalAccessException,InvocationTargetException     {         Demo  demo = new Demo();         //d.show();    //Compile time Error         //String str=d.msg; //compile Time Error         Class cls = demo.getClass();//Points to Demo Class         System.out.println("Accessing methods....");         //get Access to all the method of class         //since our Demo class has only 1 method,show().methods[] contains 1 element         Method methods[] = cls.getDeclaredMethods();         for (int i = 0; i < methods.length; i++)         {             //Prints information about method             System.out.println(methods[i].getReturnType()+" " +methods[i].getName());             methods[i].setAccessible(true);//changing the accessiblity to true             String flag1=(String)methods[i].invoke(demo);//calls show(),returns Object             System.out.println(flag1 );         }         //  Prints all the field names & values         System.out.println("Accessing Fields....");         Field fields[] = cls.getDeclaredFields();//gets all fields         for (int i = 0; i < fields.length; i++){             //prints field name             System.out.println("Field Name: " + fields[i].getName());             fields[i].setAccessible(true);//making fields accessible             String flag2=(String)fields[i].get(demo);//gets value of Demo.msg field             System.out.println(flag2);         }     } }