java string with new operator and a literal

Well, the second line won't create a new object, because you've already used the same string constant in the first line - but s1 and s will still refer to different objects.

The reason the second line won't create a new object is that string constant are pooled - if you use the same string constant multiple times, they're all resolved to the same string. There still has to be a String object allocated at some point, of course - but there'll only be one object for all uses. For example, consider this code:

int x = 0;
for (int i = 0; i < 1000000; i++) {
    String text = "Foo";
    x += text.length();
}

This will not create a million strings - the value of text will be the same on every iteration of the loop, referring to the same object each time.

But if you deliberately create a new String, that will definitely create a new object - just based on the data in the existing one. So for example:

String a = new String("test");
String b = new String("test");
String x = "test";
String y = "test";
// Deliberately using == rather than equals, to check reference equality
System.out.println(a == b); // false
System.out.println(a == x); // false
System.out.println(x == y); // true

Or to put it another way, the first four lines above are broadly equivalent to:

String literal = "test";
String a = new String(literal);
String b = new String(literal);
String x = literal;
String y = literal;