Equality for strings in Java

Prova.java

/* Run with:
     javac Prova.java && java Prova
*/
class Prova {
    public static void main(String[] args) {
        StringBuilder o = new StringBuilder("o");

        System.out.println("\"pippo\" == \"pippo\" ~~> " + ( "pippo" == "pippo") );
        System.out.println("\"pippo\" == \"pipp\" + \"o\" ~~> " + ( "pippo" == "pipp" + "o") );
        System.out.println("\"pippo\" == \"pipp\" + o ~~> " + ( "pippo" == "pipp" + o) );
        System.out.println("\"pippo\".equals(\"pipp\" + o) ~~> " + ( "pippo".equals("pipp" + o)) );
    }
}

/* Results

"pippo" == "pippo" ~~> true
"pippo" == "pipp" + "o" ~~> true
"pippo" == "pipp" + o ~~> false
"pippo".equals("pipp" + o) ~~> true

*/