Question

I’m wondering if a new object is creating here:

String obj;
if(obj == "") {
}

and here:

if(obj.equals("")){}

I mean is the object like new String(“”) instantiating for those both cases?

Answer 1

Kind of.

You’re right that the program will actually reference a full String object, containing the value "". However, this isn’t strictly created at the point the method is invoked. The Strings for (compile-time constant) string literals are created in a JVM-wide constant pool when the class is loaded into the VM, and identical constants share the same strings.

Since there’s almost certainly a class in the JVM itself that references the empty string literal, the string pool will already contain the object corresponding to "" and so your class won’t actually cause a new object to be created.