public class ParentClass {

}
public class ChildClass extends ParentClass{

}
public class Test {
	public void testOverLoad(ParentClass cls){
		System.out.println("It's ParentClass");
	}
	public void testOverLoad(ChildClass cls){
		System.out.println("It's ChildClass");
	}
	public static void main(String[] args) {
		Test test = new Test();
		ParentClass parentCls = new ParentClass();
		ParentClass childCls = new ChildClass();
		
		test.testOverLoad(parentCls);
		test.testOverLoad(childCls);
	}
}//源代码片段来自云代码http://yuncode.net