题解 | #实现抽象方法#

import java.util.Scanner;

public class Main {

public static void main(String[] args) {
    // Sub是需要你定义的子类
    Base base = new Sub();

    Scanner scanner = new Scanner(System.in);
    while (scanner.hasNextInt()) {
        int x = scanner.nextInt();
        int y = scanner.nextInt();
        base.setX(x);
        base.setY(y);
        System.out.println(base.calculate());
    }
}

}

abstract class Base {

private int x;
private int y;

public int getX() {
    return x;
}

public void setX(int x) {
    this.x = x;
}

public int getY() {
    return y;
}

public void setY(int y) {
    this.y = y;
}

public int calculate() {
    if (avg() == 0) {
        return 0;
    } else {
        return sum() / avg();
    }
}

/**
 * 返回x和y的和
 */
public abstract int sum();

/**
 * 返回x和y的平均值
 */
public abstract int avg();

}

class Sub extends Base { @Override public int sum() { return getX()+getY(); }

@Override
public int avg() {
    return (getX()+getY())/2;
}

}