String s1 = "java";

String s2 = new String("java");

class Ideone
{
public static void main (String[] args) throws java.lang.Exception
{
    String s1 = new String("java");
    System.out.println(s1.toUpperCase());

    String s2 = "java";
    System.out.println(s2.toUpperCase());
}
 }

String s1="java"   // will store in string pool
String s2=new String("java");  //will store in heap