how can pass primitive type reference in java? instance, how make int passed method modifiable? there isn't way pass primitive directly reference in java. a workaround instead pass reference instance of wrapper class, contains primitive member field. such wrapper class extremely simple write yourself: public class intref { public int value; } but how pre-built wrapper classes, don't have write our own? ok: the apache commons-lang mutable* classes: advantages : performance single threaded use. completeness. disadvantages : introduces third-party library dependency. no built-in concurrency controls. representative classes : mutableboolean , mutablebyte , mutabledouble , mutablefloat , mutableint , mutablelong , mutableobject , mutableshort . the java.util.concurrent.atomic atomic* classes: advantages : part of standard java (1.5+) api. built-in concurrency controls. disadvantages : small performance hit when used in single-threaded setting. ...