java.lang.reflect.Field.set() Method Example

Description

The java.lang.reflect.Field.set(Object obj, Object value) method sets the field represented by this Field object on the specified object argument to the specified new value. The new value is automatically unwrapped if the underlying field has a primitive type.

Declaration

Following is the declaration for java.lang.reflect.Field.set(Object obj, Object value) method.

public void set(Object obj, Object value) 
   throws IllegalArgumentException, IllegalAccessException

Parameters

• obj − the object whose field should be modified.

• value − the new value for the field of obj being modified.

Returns

true if and only if this field is a synthetic field as defined by the Java Language Specification.

Exceptions

• IllegalAccessException − if this Field object is enforcing Java language access control and the underlying field is inaccessible.

• IllegalArgumentException − if the specified object is not an instance of the class or interface declaring the underlying field (or a subclass or implementor thereof).

• NullPointerException − if the specified object is null and the field is an instance field.

• ExceptionInInitializerError − if the initialization provoked by this method fails.

Example

The following example shows the usage of java.lang.reflect.Field.set(Object obj, Object value) method.

package com.tutorialspoint;

import java.lang.reflect.Field;

public class FieldDemo {

   public static void main(String[] args) throws NoSuchFieldException, 
      SecurityException, IllegalArgumentException, IllegalAccessException {
          
      SampleClass sampleObject = new SampleClass();
            
      Field field = SampleClass.class.getField("sampleField");
      
      field.set(sampleObject, 7);
      
      System.out.println(field.getInt(sampleObject));
   }
}

class SampleClass {
   public static int sampleField = 5;
}

Let us compile and run the above program, this will produce the following result −

7