public class CharCount {
    public static void Charcount(String string) {
        if (string == null)
            return;
        int[] count = new int[string.length()];

        for (int i = 0; i < count.length; i++) {
            // 将字符串中索引字符存在临时变量中
            char mid = string.charAt(i);
            for (int j = 0; j < count.length; j++) {
                if (mid == string.charAt(j))
                    count[i]++;
            }
        }
        // 得到次数最多的字符
        int index = 0;
        int max = count[0];
        for (int i = 0; i < count.length; i++) {
            if (max < count[i]) {
                max = count[i];
                index = i;
            }
        }
        System.out.println();
        System.out.println("字符=" + string.charAt(index));
        System.out.println("次数=" + count[index]);
    }
    public static void main(String[] args) {
        Charcount("ABAACGDHGSTHJHH");
    }
}

import java.util.ArrayList;

public class CharCount {
    public static void Charcount(String string) {
        //ArrayList 保存字符串中出现的字符
        ArrayList list=new ArrayList(string.length());
        for(int i=0;i<string.length();i++){
            //只要表中不包含，将它添加到表中
            if(!list.contains(string.charAt(i))){
                list.add(string.charAt(i));
            }
        } 
        int[] count = new int[list.size()];
        //这里外循环就不用遍历整个字符串，仅仅按照List表中所保存的字符进行遍历
        for(int i=0;i<list.size();i++){
            char mid=(Character) list.get(i);
            for(int j=0;j<string.length();j++){
                if(mid==string.charAt(j)){
                    count[i]++;
                }
            }
        }
        int index = 0;
        int max = count[0];
        for (int i = 0; i < count.length; i++) {
            if (max < count[i]) {
                max = count[i];
                index = i;
            }
        }
        System.out.println("字符串中出现的字符：");
        for(int k=0;k<list.size();k++)
        {
            System.out.print(list.get(k)+" ");
        }
        System.out.println();
        System.out.println("字符" + list.get(index)+"出现的次数最多");
        System.out.println("共出现次数为： " + count[index]);
    }
    
    
    public static void main(String[] args) {
        Charcount("ABAACGDHGSTHJHH");
    }
}