Constructors for Strings and the objects used to wrap primitives should never be used. Doing so is less clear and uses more memory than simply using the desired value in the case of strings, and using valueOf for everything else.

Further, these constructors are deprecated in Java 9, which is an indication that they will eventually be removed from the language altogether.

Noncompliant Code Example

String empty = new String(); // Noncompliant; yields essentially "", so just use that.
String nonempty = new String("Hello world"); // Noncompliant
Double myDouble = new Double(1.1); // Noncompliant; use valueOf
Integer integer = new Integer(1); // Noncompliant
Boolean bool = new Boolean(true); // Noncompliant

Compliant Solution

String empty = "";
String nonempty = "Hello world";
Double myDouble = Double.valueOf(1.1);
Integer integer = Integer.valueOf(1);
Boolean bool = Boolean.valueOf(true);