ackage day0415;
import java.util.Arrays;

public class CardsPractice {
    public static void main(String[] args) {
        Card[] cards = new Card[54];
        int i=0;
        for(int rank = Card.THREE;rank<=Card.DEUCE;rank++){
            cards[i++] = new Card(Card.DIAMOND,rank);
            cards[i++] = new Card(Card.CLUB,rank);
            cards[i++] = new Card(Card.HEAT,rank);
            cards[i++] = new Card(Card.SPADE,rank);
        }
        cards[i++] = new Card(Card.JOKER,Card.BLACK);
        cards[i++] = new Card(Card.JOKER,Card.COLOR);//生成牌
    }
    System.out.println(cards.lenth);
}
class Card{
    private int rank;//点数
    private int suit;//花色
    /** 方块*/
    public final static int DIAMOND = 0;
    /** 梅花*/
    public final static int CLUB = 1;
    /** 红桃*/
    public final static int HEAT = 2;
    /** 黑桃*/
    public final static int SPADE = 3;
    /** 王*/
    public final static int JOKER = 4;
   
    public final static int THREE = 0;
    public final static int FOUR  = 1;
    public final static int FIVE = 2;
    public final static int SIX = 3;
    public final static int SEVEN = 4;
    public final static int EIGHT = 5;
    public final static int NINE = 6;
    public final static int TEN = 7;
    public final static int JACK = 8;
    public final static int QUEEN = 9;
    public final static int KING = 10;
    public final static int ACE = 11;
    public final static int DEUCE = 12;
    public final static int BLACK = 13;
    public final static int COLOR = 14;
   
    Card(int suit,int rank){
        this.suit = suit;
        this.rank = rank;
    }
    public int getSuit(){
        return this.suit;
    }
    public int getRank(){
        return this.rank;
    }
}

问题出在System.out.println(cards.lenth);
编译提示需要标识符，没想明白错在哪里？

System.out.println(cards.lenth);要加在方法体里

还是不太明白，是放的位置错了吗？

我明白了，是要放到main()方法里，谢谢指点