Java没有大题题

interface A {

    double f(double x, double y);

}

class B implements A {

    public double f(double x, double y) {

        return x * y;

    }

}

public class Test {

    public static void main(String[] args) {

        A a = new B();

        System.out.println(a.f(3, 5));

    }

}

interface Com {

    int add(int a, int b);

}

abstract class A {

    abstract int add(int a, int b);

}

class B extends A implements Com {

    public int add(int a, int b) {

        return a + b;

    }

}

public class Test {

    public static void main(String[] args) {

        B b = new B();

        Com com = b;

        System.out.println(com.add(12, 6));

        A a = b;

        System.out.println(a.add(10, 5));

    }

}

class A {

    double f(double x, double y) { return x + y; }

    static int g(int n) { return n * n; }

}

class B extends A {

    double f(double x, double y) {

        double m = super.f(x, y);

        return m + x * x;

    }

    static int g(int n) {

        int m = A.g(n);

        return m + n;

    }

}

public class Test {

    public static void main(String[] args) {

        B b = new B();

        System.out.println(b.f(10.0, 8.0));

        System.out.println(b.g(3));

    }

}

class A {

    void a() { System.out.println("a"); }

}

class B extends A {

    void a() { System.out.println("b"); }

}

public class Test {

    public static void main(String[] args) {

        A x = new B();

        x.a();

    }

}

class B {

    int x = 100, y = 200;

    void setX(int x) { x = x; }

    void setY(int y) { this.y = y; }

    int getXYSum() { return x + y; }

}

public class Test {

    public static void main(String[] args) {

        B b = new B();

        b.setX(-100);

        b.setY(-200);

        System.out.println("sum=" + b.getXYSum());

    }

}

class B {

    int n;

    static int sum = 0;

    void setN(int n) { this.n = n; }

    int getSum() {

        for (int i = 1; i <= n; i++) {

            sum = sum + i;

        }

        return sum;

    }

}

public class Test {

    public static void main(String[] args) {

        B b1 = new B();

        B b2 = new B();

        b1.setN(3);

        int s1 = b1.getSum();

        b2.setN(5);

        int s2 = b2.getSum();

        System.out.println("sum=" + (s1 + s2));

    }

}

class Tom {

    private int x = 120;

    protected int y = 20;

    int z = 11;

    private void f() { x = 88; System.out.println(x); }

    void g() { x = 99; System.out.println(x); }

}

public class Test {

    public static void main(String[] args) {

        Tom tom = new Tom();

        tom.x = 22;    // 代码1

        tom.y = 33;    // 代码2

        tom.z = 55;    // 代码3

        tom.f();       // 代码4

        tom.g();       // 代码5

    }

}