Difference Between Java Operator == and equals() Method

Comparing Strings

In Java, == and equals() are used when comparing strings, but they have different meanings.
== is a comparison operator that compares address values, while the equals() method compares the content itself, that is, the data value. Therefore, they should be used differently depending on the situation.

package com.devkuma.basic.string;

public class StringEquals {
    public static void main(String[] args) {
        String a = "devkuma";
        String b = "devkuma";

        String c = new String("devkuma");
        String d = new String("devkuma");

        System.out.println(a == b);  // true
        System.out.println(b == c);  // false
        System.out.println(c == d);  // false

        System.out.println(a.equals(b));  // true
        System.out.println(b.equals(c));  // true
        System.out.println(c.equals(d));  // true
    }
}

Execution result:

true
false
false
true
true
true

The detailed explanation of the result values is as follows.

Expression	Result	Description
`a == b`	`true`	Because of the string constant pool, the same address value is assigned to `a` and `b`, so the comparison result is `true`.
`b == c`	`false`	`b` is assigned an address value from the string constant pool, while `c` is assigned a new address value by the `new` operator, so the comparison result is `false`.
`c == d`	`false`	`c` is assigned a new address value by the `new` operator, and `d` is also assigned a new address value by the `new` operator, so the comparison result is `false`.
`a.equals(b)`	`true`	Only the values of `a` and `b` are compared, so the result is `true`.
`b.equals(c)`	`true`	Only the values of `b` and `c` are compared, so the result is `true`.
`c.equals(d)`	`true`	Only the values of `c` and `d` are compared, so the result is `true`.

References

Java String constant pool|devkuma