String s = s1 + s2;（s1和s2是字符串文字）从何处返回？ 堆或池

Question

    String s1="abc";                 //pool
    String s2="abccde";              //pool
    String s3="cde";                 //pool
    String s4=s1+s3;                 //heap
    String s5=new String("abccde");  //heap

    System.out.println(s2==s4);
    System.out.println(s4==s5);
    System.out.println(s2==s5);

I was expecting false,true false BUT got all false in result. While i tried using .intern(); in s4 i got true for s2==s4 meaning after intern(); it returned from pool so earlier it was returning from heap, so why not s4==s5 is giving true?

Thanks

Answer 1

Because new always creates a new object and has no chance of returning one from a pool? It's a constructor, not a factory method like intern().

Answer 2

None of those will ever identity equal s5 , as you explicitly used the new keyword.

If the compiler can determine that s1 and s3 are literal constants, it will treat the concat as a literal constant . However, it is not a given that the compiler can make that determination.