Operands.java

import java.util.Objects;
import java.util.Arrays;


interface Operand {
	Operand neg();
	Operand add(Int that);
	Operand add(Decimal that);
	Operand add(Operand that);
	Operand mult(Int that);
	Operand mult(Decimal that);
	Operand mult(Operand that);
	Operand sub(Int that);
	Operand sub(Decimal that);
	Operand sub(Operand that);
}

class Int implements Operand {
	final int value;
	Int(int value) { this.value = value; }
	public Int neg(){ return new Int(-this.value); }
	public Int add(Int that) { return new Int(this.value + that.value); }
	public Decimal add(Decimal that) { return new Decimal(this.value + that.value); }
	public Operand add(Operand that) { return that.add(this); }
	public Int mult(Int that) { return new Int(this.value * that.value); }
	public Decimal mult(Decimal that) { return new Decimal(this.value * that.value); }
	public Operand mult(Operand that) { return that.mult(this); }
	public Int sub(Int that) { return new Int(this.value - that.value); }
	public Decimal sub(Decimal that) { return new Decimal(this.value - that.value); }
	public Operand sub(Operand that) { return that.neg().add(this); }
	public String toString() { return String.valueOf(this.value); }
}

class Decimal implements Operand {
	final double value;
	Decimal(double value) { this.value = value; }
	public Decimal neg(){ return new Decimal(-this.value); }
	public Decimal add(Int that) { return new Decimal(this.value + that.value); }
	public Decimal add(Decimal that) { return new Decimal(this.value + that.value); }
	public Operand add(Operand that) { return that.add(this); }
	public Decimal mult(Int that) { return new Decimal(this.value * that.value); }
	public Decimal mult(Decimal that) { return new Decimal(this.value * that.value); }
	public Operand mult(Operand that) { return that.mult(this); }
	public Decimal sub(Int that) { return new Decimal(this.value - that.value); }
	public Decimal sub(Decimal that) { return new Decimal(this.value - that.value); }
	public Operand sub(Operand that) { return that.neg().add(this); }
	public String toString() { return String.valueOf(this.value); }
}



public class TestDrive {

	public static void main(String[] args) {

		Operand a = new Int(10);
		Operand b = new Int(10);
		Operand c = new Decimal(10.0);
		Operand d  = new Int(20);

		Operand x = a.mult(b).mult(c).mult(d);
		Operand y = b.mult(a);

		System.out.println(x); //yields 20000.0
		System.out.println(y); //yields 100

		Operand m = new Int(1);
		Operand n = new Int(9);

		Operand q = m.sub(n); 
		Operand t = n.sub(m); 

		System.out.println(q); //yields -8
		System.out.println(t); //yeilds 8
	}
}