Boxing is the process of putting a primitive value into a wrapper object, such as creating an Integer to hold an int
value. Unboxing is the process of retrieving the primitive value from such an object. Since the original value is unchanged during boxing and
unboxing, there is no point in doing either when not needed.
Instead, you should rely on Java’s implicit boxing/unboxing to convert from the primitive type to the wrapper type and vice versa, for better
readability.
Noncompliant code example
public void examinePrimitiveInt(int a) {
//...
}
public void examineBoxedInteger(Integer a) {
// ...
}
public void func() {
int primitiveInt = 0;
Integer boxedInt = Integer.valueOf(0);
double d = 1.0;
int dIntValue = Double.valueOf(d).intValue(); // Noncompliant; should be replaced with a simple cast
examinePrimitiveInt(boxedInt.intValue()); // Noncompliant; unnecessary unboxing
examinePrimitiveInt(Integer.valueOf(primitiveInt)); // Noncompliant; boxed int will be auto-unboxed
examineBoxedInteger(Integer.valueOf(primitiveInt)); // Noncompliant; unnecessary boxing
examineBoxedInteger(boxedInt.intValue()); // Noncompliant; unboxed int will be autoboxed
}
Compliant solution
public void examinePrimitiveInt(int a) {
//...
}
public void examineBoxedInteger(Integer a) {
// ...
}
public void func() {
int primitiveInt = 0;
Integer boxedInt = Integer.valueOf(0);
double d = 1.0;
int dIntValue = (int) d;
examinePrimitiveInt(primitiveInt);
examinePrimitiveInt(boxedInt);
examineBoxedInteger(primitiveInt);
examineBoxedInteger(boxedInt);
}
