Tricky equals() in Java

Behavior of equal() in Java with different Objects

Integer class

Integer i2 = new Integer(100);

Integer i3 = 100;

System.out.println(i2.equals(i3));

public boolean equals(Object paramObject) {

            if (paramObject instanceof Integer)

                  return (this.value == ((Integer) paramObject).intValue());

            return false;

      }

All wrapper classes overriding equals() and thus checking actual value instead of addresses.

String class

 public boolean equals(Object paramObject) {

              if (this == paramObject)

                     return true;

              if (paramObject instanceof String) {

                     String str = (String) paramObject;

                     int i = this.value.length;

                     if (i == str.value.length) {

                           char[] arrayOfChar1 = this.value;

                           char[] arrayOfChar2 = str.value;

                           for (int j = 0; i-- != 0; ++j)

                                  if (arrayOfChar1[j] != arrayOfChar2[j])

                                         return false;

                           return true;

                     }

              }

              return false;

       }

Object Class

public boolean equals(Object paramObject) {

              return (this == paramObject);

       }

public class EqualsMethod {

     public static void main(String[] args) {

           Integer i1 = new Integer(200);

           Integer i2 = 200;

           Integer i3 = new Integer(200);

           System.out.println("--equals() for Integer Object--");

           // Checking address and not values

           System.out.println(i1 == i2);

           // equals() Checks values thus result is true

           System.out.println(i1.equals(i2));

           System.out.println(i1.equals(i3));

           System.out.println("--equals() for Build In Object--");

           Employeee e1 = new Employeee("Paras", "Rohtak");

           Employeee e2 = new Employeee("Paras", "Rohtak");

           System.out.println(e1.equals(e2));

           System.out.println(e1 == e2);

          

           System.out.println("--equals() for String Object--");

           String s1= new String("Paras");

           String s2= new String("Paras");

           String s3="Paras";

           // Check values and not address

           System.out.println(s1.equals(s3));

           System.out.println(s1.equals(s2));

           System.out.println(s1==s2);

     }

}

class Employeee {

     String name;

     String address;

     Employeee(String name, String address) {

           this.name = name;

           this.address = address;

     }

}

Output:

--equals() for Integer Object--

false

true

true

--equals() for Build In Object--

false

false

366712642

--equals() for String Object--

true

true

false