半条命

Strategy

Weapon

public abstract class Weapon {
    //打斗
    public abstract void fight();
}

NoneWeapon

public class NoneWeapon extends Weapon{
    @Override
    public void fight() {
        System.out.println("空手...");
    }
}

Policeman

public class Policeman {
    private Weapon weapon;

    public Policeman(Weapon initialWeapon) {
        this.weapon = initialWeapon;
    }

    public void changeWeapon(Weapon newWeapon) {
        this.weapon = newWeapon;
    }

    public void useWeapon(){
        this.weapon.fight();
    }
}

Hostage

public class Hostage extends NoneWeapon{
    private Weapon weapon;

    public Hostage() {
    }

    public Hostage(Weapon initialWeapon) {
        this.weapon = initialWeapon;
    }

    public void changeWeapon(Weapon newWeapon) {
        this.weapon = newWeapon;
    }


    public void useWeapon(){
        weapon.fight();
    }
}

Dagger

public class Dagger extends Weapon{
    @Override
    public void fight() {
        System.out.println("挥舞匕首...");
    }
}

Grenade

public class Grenade extends Weapon{
    @Override
    public void fight() {
        System.out.println("抛出手雷...");
    }
}

Machincgun

public class Machincgun extends Weapon{
    @Override
    public void fight() {
        System.out.println("机关枪扫射...");
    }
}

Main

public class Main {
    public static void main(String[] args) {
        Weapon machincgun = new Machincgun();
        Weapon grenade = new Grenade();
        Weapon dagger = new Dagger();

        Policeman peter = new Policeman(dagger);
        Hostage mary = new Hostage();
        mary.useWeapon();
        while (true) {
            String s = new Scanner(System.in).next();
            char c = s.charAt(0);
            switch (c) {
                case '1': peter.changeWeapon(machincgun);break;
                case '4': peter.changeWeapon(grenade);break;
                case '3': peter.changeWeapon(dagger);break;
            }
            peter.useWeapon();
        }
    }
}