This rule is defined by the following Java class: net.sourceforge.pmd.rules.optimization.UnnecessaryWrapperObjectCreation
Example:
public int convert(String s) { int i, i2; i = Integer.valueOf(s).intValue(); // this wastes an object i = Integer.parseInt(s); // this is better i2 = Integer.valueOf(i).intValue(); // this wastes an object i2 = i; // this is better return i2; }