打印输出一个字符串中重复的字符_java输出一个字,要求输入相同的字

使用 Map

package org.feng.string;

import java.util.HashMap;
import java.util.Map;
import java.util.Random;

/**
 * Created by Feng on 2020/1/10 8:48
 * CurrentProject's name is java8
 * 打印输出一个字符串中重复的字符：
 * 字符串短的时候，时间较长、但是稳定。字符串长时，也是稳定的。
 * @author Feng
 */
public class StringDemo {
    public static void main(String[] args) {
        StringDemo demo = new StringDemo();
        // 生成字符串
        String item = demo.createStringByLength(10000);
        System.out.println(item);

        long mapBeginTime = System.currentTimeMillis();
        demo.printRepeatCharByMap(item);
        long mapEndTime = System.currentTimeMillis();
        System.out.println("花费时间：" + (mapEndTime - mapBeginTime));
    }

    /**
     * 输出重复字符：通过 Map
     * @param item 目标字符串
     */
    private void printRepeatCharByMap(String item){
        if(item == null || item.isEmpty()){
            return;
        }
        char[] chars = item.toCharArray();

        Map<Character, Integer> map = new HashMap<>(16);
        for (char aChar : chars) {
            map.put(aChar, map.getOrDefault(aChar, 0) + 1);
        }

        map.forEach((key, value) -> {
            if(value > 1){
                System.out.println(key);
            }
        });
    }


    /**
     * 按照输入的长度，生成指定长度的字符串
     * 只由 [a,z] 随机组成
     * @param length 字符串长度
     * @return 目标字符串
     */
    private String createStringByLength(int length){
        StringBuilder sb = new StringBuilder(length);

        Random random = new Random();
        for (int i = 0; i < length; i++) {
            // a --> 97, z --> 122
            int num = random.nextInt(26) + 97;
            sb.append((char)num);
        }
        return sb.toString();
    }
}


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测试结果

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花费时间：73

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