Java String variable setting - reference or value?

Question

The following Java code segment is from an AP Computer Science practice exam.

String s1 = \"ab\";
String s2 = s1;
s1 = s1 + \"c\";
System.out.println(s1 + \"         


        

Answer 1

int s1 = 1;
int s2 = s1; // copies value, not reference
s1 = 42;

System.out.println(s1 + " " + s2); // prints "1 42"

Doesn't print "1 42" but "42 1".Take each discrete line into consideration.First s1 assigns 1, then s2 assigns s1, which is 1 up until now(suppose java didn't see the third line yet.) Then java sees the third line and immediately changes s1 into 42.After that java was told to print what it knows so far, and that is s1 is 42 and s2 is 1(the old s1).

As for the String the same thing happens.

String s1 = "ab";
String s2 = s1;
s1 = s1 + "c";
System.out.println(s1 + " " + s2);// prints "abc ab".

Fort String it doesn't necessarily changes s1 but rather s1 now refers to a new String object in the heap memory, but the old "ab" object is still there, with a new reference of s2!