set、get方法：间接访问private修饰的变量，对传过来的值可做判断处理。
toString:决定输出类时的内容。

下面对前几天写的扑克牌demo进行改进：

1.新建4个类，分别为Constants，MyClass，Poker，PokerManager，其中Constants保存扑克牌的花色和点数，Poker保存每一张牌，PokerManager为扑克牌功能的集合，MyClass为主类。

2.Constant:定义字符串保存扑克牌的花色和点数即可

public class Constants {
    public static final String[] DOTS = new String[]{
                  "2","3","4" ,"5","6","7","8","9","10","J","Q","K","A"
            };
    public static final String[] PICS = new String[]{
                    "♠","♣","♦","♥"
            };
}

3.Poker：定义扑克牌属性，并定义Poker类的构造方法和其get、set方法，并修改需要的toString方法

public class Poker {
    private String dot;
    private String pic;

    public Poker(String dot, String pic) {
        this.dot = dot;
        this.pic = pic;
    }

    public String getDot() {
        return dot;
    }

    public void setDot(String dot) {
        this.dot = dot;
    }

    public String getPic() {
        return pic;
    }

    public void setPic(String pic) {
        this.pic = pic;
    }

    @Override
    public String toString() {
        return dot+pic+" ";
    }
}

4.PokerManager：实现生成、显示、打乱一副牌的方法

public class PokerManager {
    //保存一副牌
    private ArrayList<Poker> pokers;

    //构造方法
    public PokerManager() {
        pokers = new ArrayList<>();
    }

    //生成一副牌
    public void generate(){
        for (int i = 0;i<Constants.DOTS.length;i++){
            String dot = Constants.DOTS[i];
            for (int j = 0;j<Constants.PICS.length;j++){
                String pic = Constants.PICS[j];
                //创建一张牌保存
                Poker poker = new Poker(dot,pic);
                //保存
                int index = i*4+j;
                pokers.add(poker);
            }
        }
    }

    //显示一副牌
    public void show(){
        int index = 1;
        for(Poker poker :pokers){
            System.out.print(poker);
            if(index%8 == 0){
                System.out.println("");
            }
            index++;
        }
    }

    //打乱一副牌
    public void shuffle(){
        Collections.shuffle(pokers);
    }

}

5.MyClass：即为整个程序的运行逻辑

public class MyClass {
    public static void main(String[] args){
        //创建管理器
        PokerManager manager = new PokerManager();
        //生成一幅牌
        manager.generate();
        //打乱一副牌
        manager.shuffle();
        //显示
        manager.show();

    }

至此，即可开始您的慈善赌王事业。