字符串排序与统计

超、凢脫俗 2022-06-16 10:24 315阅读 0赞

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 {
    
    
    	@Test
    	public 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(){
    			@Override
    			public 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();
    	}
    
    }