Reflection Commit

Author: suyash248

Accessing & modifying private data members outside class/Privateobject.java

@@ -0,0 +1,24 @@
+import java.lang.reflect.*;
+public class Privateobject
+{
+ private String privatestring=null;                            /* In this program one class is public so you have to save the .java file same as 
+ public Privateobject(String privatestring)                   the name of the public class name (ie. 'Privateobject.java') because implicit 
+ {                                                                                         compiling is done here.  */
+  this.privatestring=privatestring;
+ }
+}
+class Temp
+{
+ public static void main(String... s)throws Exception
+ {
+  Privateobject privateobject=new Privateobject("The private value");
+  Class c=Privateobject.class;
+  Field privatestringfield=c.getDeclaredField("privatestring");         /* If the field passed in the form of string in 'getDeclaredFeild()'
+  privatestringfield.setAccessible(true);                                             method is not found then 'NoSuchFileFoundexception' occurs. */
+  String fieldvalue=(String)privatestringfield.get(privateobject);
+  System.out.println("Field value="+fieldvalue);
+ }
+}
+
+/*OUTPUT-
+Field value=The private value  */

Accessing & modifying private data members outside class/privateobject-int-static/Privateobject.java

@@ -0,0 +1,29 @@
+import java.lang.reflect.*;
+public class Privateobject
+{
+ private static int privateint=5;                            
+}
+class Temp
+{
+ public static void main(String... s)throws Exception
+ {
+  Privateobject privateobject=new Privateobject();
+  Class c=Privateobject.class;
+  Field privatefield=c.getDeclaredField("privateint");         
+  privatefield.setAccessible(true);                 
+  int fieldvalue=(int)privatefield.get(privateobject);
+  System.out.println("Field value="+fieldvalue);
+
+  //Code for modifying the static private field-
+
+  System.out.println("changed value of private field is : ");
+  privatefield.set(null,10);
+  int fieldvalue1=(int)privatefield.get(privateobject);
+  System.out.println("Field value="+fieldvalue1);
+ }
+}
+
+/* OUTPUT-
+Field value=5
+changed value of private field is :
+Field value=10  */

Accessing & modifying private data members outside class/privateobject-int/Privateobject.java

@@ -0,0 +1,33 @@
+import java.lang.reflect.*;
+public class Privateobject
+{
+ private int privateint=0;                            
+ public Privateobject(int privateint)                  
+ {        
+  this.privateint=privateint;
+ }
+}
+class Temp
+{
+ public static void main(String... s)throws Exception
+ {
+  Privateobject privateobject=new Privateobject(5);
+  Class c=Privateobject.class;
+  Field privatefield=c.getDeclaredField("privateint");         
+  privatefield.setAccessible(true);                 
+  int fieldvalue=(int)privatefield.get(privateobject);
+  System.out.println("Field value="+fieldvalue);
+
+  //Code for modifying the value of private field-
+  
+  System.out.println("changed value of private field is : ");
+  privatefield.set(privateobject,10);
+  int fieldvalue1=(int)privatefield.get(privateobject);
+  System.out.println("Field value="+fieldvalue1);
+ }
+}
+
+/* OUTPUT-
+Field value=5
+changed value of private field is :
+Field value=10  */

Accessing & modifying private data members outside class/privateobject-string/Privateobject.java

@@ -0,0 +1,33 @@
+import java.lang.reflect.*;
+public class Privateobject
+{
+ private String privatestring=null;                            
+ public Privateobject(String privatestring)                  
+ {        
+  this.privatestring=privatestring;
+ }
+}
+class Temp
+{
+ public static void main(String... s)throws Exception
+ {
+  Privateobject privateobject=new Privateobject("The private value");
+  Class c=Privateobject.class;
+  Field privatestringfield=c.getDeclaredField("privatestring");         
+  privatestringfield.setAccessible(true);                 
+  String fieldvalue=(String)privatestringfield.get(privateobject);
+  System.out.println("Field value="+fieldvalue);
+ 
+  //Code for modifying the contents of private field-
+  
+  System.out.println("changed value of private field is : ");
+  privatestringfield.set(privateobject,"changed value");
+  String fieldvalue1=(String)privatestringfield.get(privateobject);
+  System.out.println("Field value="+fieldvalue1);
+ }
+}
+
+/*  OUTPUT-
+Field value=The private value
+changed value of private field is :
+Field value=changed value  */

Accessing private methods outside class/2 methods having same arguments/Privateobject.java

@@ -0,0 +1,42 @@
+import java.lang.reflect.*;
+class Privateobject
+{
+ private String privatestring=null;
+ public Privateobject(String privatestring)
+ {
+  this.privatestring=privatestring;
+ }
+ private String getprivatestring(int a,char b)
+ {
+  System.out.println("a="+a);
+  System.out.println("b="+b);
+  System.out.println("This is getprivatestring");
+  return this.privatestring;
+ }
+ private String getprivatestring1(int a1,char b1)
+ {
+  System.out.println("a1="+a1);
+  System.out.println("b1="+b1);
+  System.out.println("This is getprivatestring1");
+  return this.privatestring;
+ }
+}
+class Temp
+{
+ public static void main(String... w)throws Exception
+ {
+  Privateobject privateobject=new Privateobject("The private value");
+  Object o[]={5,'c'};
+  Class c[]={int.class,char.class};
+  Method privatestringmethod=Privateobject.class.getDeclaredMethod("getprivatestring",c);
+  privatestringmethod.setAccessible(true);
+  String returnvalue=(String)privatestringmethod.invoke(privateobject,o);
+  System.out.println("Return Value="+returnvalue);
+ }
+}
+
+/*  OUTPUT-
+a=5
+b=c
+This is getprivatestring
+Return Value=The private value  */

Accessing private methods outside class/exception/Privateobject.java

@@ -0,0 +1,33 @@
+import java.lang.reflect.*;
+class Privateobject
+{
+ private String privatestring=null;
+ public Privateobject(String privatestring)
+ {
+  this.privatestring=privatestring;
+ }
+ private String getprivatestring(int a,char b)
+ {
+  System.out.println("a="+a);
+  System.out.println("b="+b);
+  return this.privatestring;
+ }
+}
+class Temp
+{
+ public static void main(String... w)throws Exception
+ {
+  Privateobject privateobject=new Privateobject("The private value");
+  Object o[]={5,'c'};
+  Class c[]={char.class,int.class};
+  Method privatestringmethod=Privateobject.class.getDeclaredMethod("getprivatestring",c);
+  privatestringmethod.setAccessible(true);
+  String returnvalue=(String)privatestringmethod.invoke(privateobject,o);
+  System.out.println("Return Value="+returnvalue);
+ }
+}
+
+/* OUTPUT-
+Exception in thread "main" java.lang.NoSuchMethodException: Privateobject.getprivatestring(char, int)
+        at java.lang.Class.getDeclaredMethod(Unknown Source)
+        at Temp.main(Privateobject.java:23)  */

Accessing private methods outside class/one method having different types of arguments/Privateobject.java

@@ -0,0 +1,33 @@
+import java.lang.reflect.*;
+class Privateobject
+{
+ private String privatestring=null;
+ public Privateobject(String privatestring)
+ {
+  this.privatestring=privatestring;
+ }
+ private String getprivatestring(int a,char b)
+ {
+  System.out.println("a="+a);
+  System.out.println("b="+b);
+  return this.privatestring;                                       // 'this' is optional.
+ }
+}
+class Temp
+{
+ public static void main(String... w)throws Exception
+ {
+  Privateobject privateobject=new Privateobject("The private value");
+  Object o[]={5,'c'};
+  Class c[]={int.class,char.class};
+  Method privatestringmethod=Privateobject.class.getDeclaredMethod("getprivatestring",c);
+  privatestringmethod.setAccessible(true);
+  String returnvalue=(String)privatestringmethod.invoke(privateobject,o);
+  System.out.println("Return Value="+returnvalue);
+ }
+}
+
+/*  OUTPUT-
+a=5
+b=c
+Return Value=The private value  */

Accessing private methods outside class/one method having same types of arguments/Privateobject.java

@@ -0,0 +1,28 @@
+import java.lang.reflect.*;
+class Privateobject
+{
+ private String privatestring=null;
+ public Privateobject(String privatestring)
+ {
+  this.privatestring=privatestring;
+ }
+ private String getprivatestring(int a,int b)
+ {
+  System.out.println("a="+a);
+  System.out.println("b="+b);
+  return this.privatestring;
+ }
+}
+class Temp
+{
+ public static void main(String... w)throws Exception
+ {
+  Privateobject privateobject=new Privateobject("The private value");
+  Object o[]={5,10};
+  Class c[]={int.class,int.class};
+  Method privatestringmethod=Privateobject.class.getDeclaredMethod("getprivatestring",c);
+  privatestringmethod.setAccessible(true);
+  String returnvalue=(String)privatestringmethod.invoke(privateobject,o);
+  System.out.println("Return Value="+returnvalue);
+ }
+}

Accessing private methods outside class/overloaded methods/Privateobject.java

@@ -0,0 +1,44 @@
+import java.lang.reflect.*;
+class Privateobject
+{
+ private String privatestring=null;
+ public Privateobject(String privatestring)
+ {
+  this.privatestring=privatestring;
+ }
+ private String getprivatestring(int a,char b)
+ {
+  System.out.println("a="+a);
+  System.out.println("b="+b);
+  System.out.println("This is getprivatestring");
+  return this.privatestring;
+ }
+ private String getprivatestring(int a1,char b1,String c1)
+ {
+  System.out.println("a1="+a1);
+  System.out.println("b1="+b1);
+  System.out.println("c1="+c1);
+  System.out.println("This is getprivatestring");
+  return this.privatestring;
+ }
+}
+class Temp
+{
+ public static void main(String... w)throws Exception
+ {
+  Privateobject privateobject=new Privateobject("The private value");
+  Object o[]={5,'c',"Hello"};
+  Class c[]={int.class,char.class,String.class};
+  Method privatestringmethod=Privateobject.class.getDeclaredMethod("getprivatestring",c);
+  privatestringmethod.setAccessible(true);
+  String returnvalue=(String)privatestringmethod.invoke(privateobject,o);
+  System.out.println("Return Value="+returnvalue);
+ }
+}
+
+/*  OUTPUT-
+a1=5
+b1=c
+c1=Hello
+This is getprivatestring
+Return Value=The private value  */

Accessing private methods outside class/private method without arguments/Privateobject.java

@@ -0,0 +1,27 @@
+import java.lang.reflect.*;
+class Privateobject
+{
+ private String privatestring=null;
+ public Privateobject(String privatestring)
+ {
+  this.privatestring=privatestring;
+ }
+ private String getprivatestring()
+ {
+  return this.privatestring;
+ }
+}
+class Temp
+{
+ public static void main(String... w)throws Exception
+ {
+  Privateobject privateobject=new Privateobject("The private value");
+  Method privatestringmethod=Privateobject.class.getDeclaredMethod("getprivatestring",null);
+  privatestringmethod.setAccessible(true);
+  String returnvalue=(String)privatestringmethod.invoke(privateobject,null);
+  System.out.println("Return Value="+returnvalue);
+ }
+}
+
+/* OUTPUT-
+Return Value=The private value  */

Accessing private methods outside class/private static method/Privateobject.java

@@ -0,0 +1,28 @@
+import java.lang.reflect.*;
+class Privateobject
+{
+ private static String getprivatestring(int a,char b,String s)
+ {
+  System.out.println("a="+a);
+  System.out.println("b="+b);
+  return s;
+ }
+}
+class Temp
+{
+ public static void main(String... w)throws Exception
+ {
+  Privateobject privateobject=new Privateobject();
+  Object o[]={5,'c',"Hello"};
+  Class c[]={int.class,char.class,String.class};
+  Method privatestringmethod=Privateobject.class.getDeclaredMethod("getprivatestring",c);
+  privatestringmethod.setAccessible(true);
+  String returnvalue=(String)privatestringmethod.invoke(null,o);
+  System.out.println("Return Value="+returnvalue);
+ }
+}
+
+/*  OUTPUT-
+a=5
+b=c
+Return Value=Hello  */

Class loading & static block/Cls.java

@@ -0,0 +1,17 @@
+class Cls
+{
+ public static void main(String... w)
+ {
+  try{
+  Class c=Class.forName("Temp");
+  System.out.println("This is Cls");
+  }catch(Exception e){System.out.println(e);}
+ }
+}
+
+/*  OUTPUT-
+static block
+This is Cls  
+
+First,you have to compile 'Temp.java' as well as 'Cls.java' both.If you will not compile 'Temp.java' and try to run 'Cls.java' 
+then 'java.lang.ClassNotFoundException: Temp' will occur.  */