"Boxing" is the process of putting a primitive value into a primitive-wrapper object. When that's done purely to use the wrapper class' toString method, it's a waste of memory and cycles because those methods are static, and can therefore be used without a class instance. Similarly, using the static method valueOf in the primitive-wrapper classes with a non-String argument should be avoided.

Noncompliant Code Example

int myInt = 4;
String myIntString = new Integer(myInt).toString(); // Noncompliant; creates & discards an Integer object
myIntString = Integer.valueOf(myInt).toString(); // Noncompliant

Compliant Solution

int myInt = 4;
String myIntString = Integer.toString(myInt);