读下面程序，写出程序的运行结果public class test1{public static void main(String[] args){String s1="ABC";String s2="ABC";System.out.println("s2==s1:" (s2==s1));String s3=new String("ABC");System.out.println("s3==s2:" (s3==s2));String s4=new String("ABC");System.out.println("s4==s3:" (s4==s3));}}