StringLiteralNoObject

Correction

Here is what's right.

All the following three statements are correct.

String s1 = "Hello";
String s2 = new String("Hello");
String s3 = new String(new String("Hello"));

However, the second statement uses "Hello", which already refers to a String object, as an argument to the String(String original) constructor, which copies the passed in String. Thus, it unnecessarily creates a copy of the original String literal.

The third statement is even worse: it creates a copy of "Hello", and then it creates a copy of that copy. That’s two unnecessary object allocations.

Symptoms

How do you know your students might have this misconception?

Novice students may write code like this:

public class Contact {
  private String name = new String("Duke"); // unnecessary wrapping
  private Address address = new Address("1 Java Way");
  //...
}