what does the equals() exactly comparing when you using it to compare two objects?

Question

here is the class I want to compare:

public class test
{
   private String str=null;
   private int integer=0;
   private double doubleNum=1.1; 
}

now I'm comparing it by instantiate two same classes

public class testEquals
{
   public static void main(String[] args)
   {
      test s1 = new test();
      test s2 = new test();
      System.out.print(s1.equals(s2));
   }
}

the result is

false

Answer 1

Your test class didn't override equals , so it inherits the method from Object :

The equals method for class Object implements the most discriminating possible equivalence relation on objects; that is, for any non-null reference values x and y, this method returns true if and only if x and y refer to the same object (x == y has the value true).

They aren't the same object, so false is returned.

Answer 2

looking at Object.equeals() which is what you are calling, you will see that the default implementation is comparing the object using ==, which is basically comparing the address.

http://grepcode.com/file/repository.grepcode.com/java/root/jdk/openjdk/7-b147/java/lang/Object.java#149