4.22

import java.util.Random;
abstract class BinaryOperation {
    static final int UPPER = 100;
    static final int LOWER = 0;
    private int left_operand = 0, right_operand = 0;
    private char operator = '+';
    private int value = 0;
    
    protected void generateBinaryOperation (char anOperator) {
        int left, right, result;
        Random random = new Random();
        left = random.nextInt(UPPER + 1);
        do {
            right = random.nextInt(UPPER + 1);
            result = calculate(left, right);
        } while (!(checkingCalculation(result)));
        left_operand = left;
        right_operand = right;
        operator = anOperator;
        value = result;
    }
    abstract boolean checkingCalculation(int anInteger);
    abstract int calculate(int left, int right);
    
    public int getLeftOperand() { return left_operand; }
    public int getRightOperand() { return right_operand; }
    public char getOperator() { return operator; }
    public int getResult() { return value; }
    
    public boolean equals (BinaryOperation anOperation) {
        return left_operand == anOperation.getLeftOperand() &
                right_operand == anOperation.getRightOperand() &
                operator == anOperation.getOperator();
    }
}

class AdditionOperation extends BinaryOperation {
    AdditionOperation() {
        generateBinaryOperation('+');
    }
    public boolean checkingCalculation(int anInteger) {
        return anInteger <= UPPER;
    }
    int calculate(int left, int right) {
        return left + right;
    }
}

class SubstractOperation extends BinaryOperation {
    SubstractOperation(){
        generateBinaryOperation('-');
    }
    public boolean checkingCalculation(int anInteger) {
        return anInteger <= UPPER;
    }
    int calculate(int left, int right) {
        return left - right;
    }
}

public class BinaryOperationTester {
    public static void main(String[] args) {
        BinaryOperation bop;
        for (int i = 0; i < 10; i++) {
            bop = new AdditionOperation ();
            System.out.println(bop);
        }
    }

}