我想用这些的下标来比较大小，但不知道如何去比较，如果可以的话能用这个举例就更好了

String card[]={"红桃2","红桃K","红桃Q","红桃J","红桃10","红桃9","红桃8","红桃7","红桃6","红桃5","红桃4","红桃3","红桃A","黑桃2","黑桃K","黑桃Q",
    "黑桃J","黑桃10","黑桃9","黑桃8","黑桃7","黑桃6","黑桃5","黑桃4","黑桃3","黑桃A","梅花2","梅花K","梅花Q","梅花J","梅花10","梅花9","梅花8","梅花7",
    "梅花6","梅花5","梅花4","梅花3","梅花A","方片2","方片K","方片Q","方片J","方片10","方片9","方片8","方片7","方片6","方片5","方片4","方片3","方片A","大王","小王"};

数组的下标是0开始的，你可以把牌从小到大先排好，这样牌的大小就对应了数组下标的大小

做个map映射就很简单了
"红桃2" -> 0
"红桃3" -> 1
...

这个利用到了ascii码的知识

    public static void main(String[] args) {
        String[] a = {"红桃A", "红桃3", "红桃J"};  
        System.out.println(comparePoker(a[1], a[0]));
        System.out.println(comparePoker(a[1], a[2]));
        System.out.println(comparePoker(a[2], a[0]));
    }

    public static boolean comparePoker (String var1, String var2) {
        int num1 = var1.charAt(var1.length() - 1);
        int num2 = var2.charAt(var2.length() - 1);

        if (num1 == 'A') {
            num1 = 1;
        }
        if (num2 == 'A') {
            num2 = 1;
        }
        return num1 > num2;
    }