Function Object in Java

Question

I wanna implement a javascript like method in java , is this possible ?

Say , I have a Person class :

public class Person {
 private String name ;
 priva         


        

Answer 1

You can do it with an interface and an anonymous inner class implementing it, like

Person p1 = new Person("Jenny",20);
Person p2 = new Person("Kate",22);
List pList = Arrays.asList(p1, p2);

interface Operation {
  abstract void execute(Person p);
}

public void modList(List list, Operation op) {
  for (Person p : list)
    op.execute(p);
}

modList(pList, new Operation {
  public void execute(Person p) { p.setAge(p.getAge() + 1)};
});

Note that with varargs in Java5, the call to Arrays.asList can be simplified as shown above.

Update: A generified version of the above:

interface Operation {
  abstract void execute(E elem);
}

public  void modList(List list, Operation op) {
  for (E elem : list)
    op.execute(elem);
}

modList(pList, new Operation() {
    public void execute(Person p) { p.setAge(p.getAge() + 1); }
});

Note that with the above definition of modList, you can execute an Operation on e.g. a List too (provided Student is a subclass of Person). A plain List parameter type would not allow this.