对HashMap中的实体类进行排序

客官°小女子只卖身不卖艺 2022-02-25 13:11 320阅读 0赞

package demo20130414;
    
    import java.util.Collection;
    import java.util.Collections;
    import java.util.Comparator;
    import java.util.HashMap;
    import java.util.Iterator;
    import java.util.Map;
    import java.util.Map.Entry;
    import java.util.Set;
    import java.util.ArrayList;
    import java.util.List;
    public class CharCounterDemo {
    	/**
    	 */
    	public static void main(String[] args) {
    		String str = "aabbccdderffisfalgjgosdrugnsdsduhgdsfugsdogosdjgosdig";
    		Map<Character, Integer> map = countAll(str);
    		System.out.println(map);
    		// 迭代Map： 迭代所有的key，迭代所有的value迭代Entry<key,value>
    		// 迭代所有的value，实现统计所有的字符总数
    		Collection<Integer> values = map.values();
    		Iterator<Integer> ite = values.iterator();
    		int total = 0;
    		while (ite.hasNext()) {
    			Integer n = ite.next();
    			total += n;
    			System.out.print(n + " ");
    		}
    		System.out.println("字符总数：" + total);
    		// 迭代所有的key，利用迭代所有字符实现输出统计表格
    		Set<Character> keys = map.keySet();
    		System.out.println("字符串中所有字符的个数：" + keys.size());
    		ArrayList<Character> list = new ArrayList<Character>(keys);
    		Collections.sort(list);// 自然排序
    		for (Iterator<Character> i = list.iterator(); i.hasNext();) {
    			Character ch = i.next();
    			int n = map.get(ch);
    			System.out.print(ch + ":");
    			System.out.println(n + " " + ((float) n / total) * 100 + "%");
    			// System.out.print(ch);
    		}
    	    System.out.println("照字符出现的数量排序输出:");
    	    //迭代Entry<key:Value> 实现按照字符出现的数量排序输出
    		Set<Entry<Character, Integer>> entries = map.entrySet();
    		List<Entry<Character,Integer>> entList=new ArrayList<Entry<Character,Integer>>(entries);
    		Collections.sort(entList, new ByValue());
    		for (Iterator<Entry<Character, Integer>> i = entList.iterator(); i.hasNext();) {
    				Entry<Character,Integer> entry=i.next();
    				Character ch=entry.getKey();
    				Integer n=entry.getValue();
    				System.out.print(ch + ":");
    				System.out.println(n + " " + ((float) n / total) * 100 + "%");
    		}
    	}
    
    	private static Map<Character, Integer> countAll(String str) {
    		int length = str.length();
    		Map<Character, Integer> map = new HashMap<Character, Integer>();
    		for (int i = 0; i < length; i++) {
    			char ch = str.charAt(i);
    			if (map.containsKey(ch)) {// 如果包含ch
    				int n = map.get(ch);
    				map.put(ch, n + 1);
    			} else {// 如果不包含ch
    				map.put(ch, 1);
    			}
    		}
    		return map;
    	}
    }
    class ByValue implements Comparator<Entry<Character,Integer>>{
    	public int compare(Entry<Character, Integer> o1,
    			Entry<Character, Integer> o2) {
    		// TODO Auto-generated method stub
    		return -(o1.getValue()-o2.getValue());//从大到小排列
    		//return (o1.getValue()-o2.getValue());//从小到大排列
    	}
    }