Whant is 'equals' and '==' in JAVA mean......?

[Abhishek Dhar]

Can anybody help me in explaining what do we mean by following operators in JAVA:

'equals' and '=='

Please give a brief definition about how can i use them and try to give a simple example

[Keith Lynn]

The Object class defines a method called equals that is inherited by all classes.

This method allows us to define what it means for two different objects to be meaningfully equal.

However, if a class does not override equals, then the default behavior is simply to check to see if the object reference calling the method and the object reference sent to the method refer to the same object.

Consider the following example.

public class Test25 {
   private int num;
 
   public Test25(int num) {
      this.num = num;
   }
 
   public boolean equals(Object o) {
      if (!(o instanceof Test25))
         return(false);
 
      Test25 test25 = (Test25)o;
 
      return(num == test25.num);
   }
 
   public static void main(String[] args) {
      Test25 first = new Test25(1);
      Test25 second = new Test25(1);
 
      System.out.println(first == second);
      System.out.println(first.equals(second));
   }
}

first and second refer to different objects, but they are meaningfully equal.

[Campbell Ritchie]

More about what Keith Lynn says. If you are dealing with a primitive type, you can only use the == operator.
Whenever you are trying to use an equals() method, go to the API for that class and look for its equals method. If it appears in the block headed "mothods inherited from java.lang.Object" then it hasn't been overridden and does what Keith Lynn calls default behaviour.