Difference between Initializing string with new and “ ”

Question

Which one is correct and why:

String dynamic = new String();
dynamic = \" where id=\'\" + unitId + \"\'\";

Or

String dynamic = \" where id=\'\" + unitId + \"         


        

Answer 1

String dynamic = new String();
dynamic = " where id='" + unitId + "'";

creates a binding to an empty string, and then dumps it completely by re-initializing it.

String dynamic = " where id='" + unitId + "'";

creates the binding and leaves it.

The first one is unnecessary. Just go with the direct string literal.

Answer 2

String dynamic = new String();   //created an String object
dynamic = " where id='" + unitId + "'"; //overriding reference with new value

Since string is immutable and now dynamic will store in common pool.

And

String dynamic = " where id='" + unitId + "'";

Is again a literal and stores in common pool.

So , String can be created by directly assigning a String literal which is shared in a common pool.

It is uncommon and not recommended to use the new operator to construct a String object in the heap.

So the line

String dynamic = new String();

Is redundant and allocating unnecessary memory in heap.

Don't do that.

Learn what happens in both the cases, then you come to know.

• How can a string be initialized using " "?

And finally, do not use much concatenation's with "+", cannot do much harm in lesser amount of concatenations. If you are dealing with larger amount prefer to use StringBuilder with append method.

• String concatenation in Java - when to use +, StringBuilder and concat