字符串排序与统计

统计字符串”abadcdffbaeba”中每个字符出现了多少次，按次数排序并输出。例如：c : 1，e : 1，d : 2，f : 2，b : 3，a : 4

package com.heima.question7;import static org.junit.Assert.assertEquals;import java.util.ArrayList;import java.util.Collections;import java.util.Comparator;import java.util.HashMap;import java.util.List;import java.util.Map;import org.junit.Test;public class StringStatictis {@Testpublic void test(){String originalString = "abadcdffbaeba";String resultString = stringStatictis(originalString);String expectedString = "c:1,e:1,d:2,f:2,b:3,a:4";assertEquals(expectedString,resultString);}public static void main(String[] args){String originalString = "abadcdffbaeba";String resultString = stringStatictis(originalString);String expectedString = "c:1,e:1,d:2,f:2,b:3,a:4";System.out.println(resultString);}@SuppressWarnings("unchecked")public static String stringStatictis(String originalString){char[] charArray = originalString.toCharArray();List<Character> list = new ArrayList<Character>();for(char c : charArray){list.add(c);}/** * 将统计结果存在一个Map当中，key为出现的字符，value为字符出现的次数 */Map<Character,Integer> map = new HashMap<Character,Integer>();/** * 取得并移除list中的第一个元素，将其作为key并将其与list中的其它key相比较，如果相等，则将其元素同样从list中移除， * 同时，将key所对应的value值加1 */while(list.size()>0){char key = list.remove(0);Integer value = 1 ;int newListSize = list.size();int j=0;for(int i=0;i<newListSize;i++){if(key==list.get(j)){list.remove(j);value++;}else{j++;}}map.put(key, value);}List sortList = new ArrayList(map.entrySet());/** * 对sortList中的元素进行排序： * 1.按字符出现的次数排序，出现次数多的排在后面 * 2.如果字符次数相等，则将小字符排在前面 */Collections.sort(sortList,new Comparator(){@Overridepublic int compare(Object o1, Object o2) { Map.Entry obj1 = (Map.Entry) o1; Map.Entry obj2 = (Map.Entry) o2; if((Integer)obj1.getValue()==(Integer)obj2.getValue()){ return (Character)obj1.getKey() - (Character)obj2.getKey(); }else{ return (Integer)obj1.getValue()-(Integer)obj2.getValue(); } }});StringBuilder sb = new StringBuilder();for(Object obj:sortList){Map.Entry entry = (Map.Entry)obj;sb.append(entry.getKey()+":"+entry.getValue()+",");}sb.deleteCharAt(sb.length()-1);return sb.toString();}}