passing class as an argument in java

/* Class Test*/
class Test{
int x,y;
 Test(int x,int y){
    this.x=x;
    this.y=y;
  }
 void m3(){
   System.out.println("Test's m4");
 }
}

/*class Box*/
class Box
{
	int w,h,d;
	Box(int w,int h,int d){
	   this.w=w;
	   this.h=h;
	   this.d=d;
	}
	void m1(){
	  System.out.println("Box's m1");
	}
}

/*sub class of Box*/
class BoxWt extends Box
{
	int w,h,d,wt;
	BoxWt(int w,int h,int d,int wt){
	    super(w,h,d);
		this.wt=wt;
	}
	void m2(){
	System.out.println("BoxWt's m2");
	}
}

/*Figure Abstract class*/
abstract class Figure{
 int x,y;
 Figure(int x,int y){
  this.x=x;
  this.y=y;
 }
 abstract double area();
}
class Tri extends Figure
{
  int x,y;
  Tri(int x,int y){
  super(x,y);
  }
  double area(){
    return (0.5*x*y);
  }
}

/*Class Hello*/
class Hello{
  Test m4(Box z){
    System.out.println("M4,myreturn type is test");
	Box b=new Box(1,2,3);
	return b;
  }
 /* Box m5(int x,int y,int z){
     System.out.println("m5,my return type is Box");
	 return 1;
  }*/
  void m6(BoxWt z){
    System.out.println("m6,....................");
  }
  BoxWt m7(int x,int y,int z,int wt){
    BoxWt bw=new BoxWt(x,y,z,wt);
	return bw;
  }
}

/*main class*/
class ExDemo{
	public static void main(String[] args){
	Box b=new Box(1,2,3);
	BoxWt bw=new BoxWt(4,5,6,7);
	Test t=new Test(10,20);
	Hello h=new Hello();
	Figure f;
	f=new Tri(30,40);
	}
}