java中使用map排序的实例讲解

List list = new ArrayList(map.entrySet());
Collections.sort(list, (Entry e1, Entry e2)-> {
  return e1.getKey().compareTo(e2.getKey());
});

public class SortKeysMapTest {
  public static void main(String[] args) {
    Map<String, String> map = new HashMap<>();
    map.put("2010", "jay");
    map.put("1999", "whx");
    map.put("3010", "huaxiao");
    List<Map.Entry<String,String>> list = new ArrayList<>(map.entrySet());
    Collections.sort(list, (Map.Entry e1, Map.Entry e2)-> {
        return e1.getKey().toString().compareTo(e2.getKey().toString());
    });

    for (Map.Entry entry : list) {
      System.out.println("key:" + entry.getKey() + ",value:" + entry.getValue());
    }
 
  }
}

import java.util.Comparator;
import java.util.Iterator;
import java.util.Map;
import java.util.Set;
import java.util.TreeMap;
public class TreeMapTest {
public static void main(String[] args) {
Map<String, String> map = new TreeMap<String, String>(
new Comparator<String>() {
public int compare(String obj1, String obj2) {
// 降序排序
return obj2.compareTo(obj1);
}
});
map.put("b", "ccccc");
map.put("d", "aaaaa");
map.put("c", "bbbbb");
map.put("a", "ddddd");
Set<String> keySet = map.keySet();
Iterator<String> iter = keySet.iterator();
while (iter.hasNext()) {
String key = iter.next();
System.out.println(key + ":" + map.get(key));
}
}
}

import java.util.Comparator;
import java.util.Scanner;
import java.util.TreeMap;
import problem2.Screen;

public class TestScreen {
 final static int MAX_NUM = 8;
 public static void main(String []args){
  TreeMap<Screen,Integer> res = new TreeMap<Screen, Integer>(new Comparator<Screen>() {
   @Override
   public int compare(Screen screen1, Screen t1) { // 定义TreeMap的排序方法
    return screen1.compareTo(t1); // TreeMap的排序方法是：调用screen的比较方法
   }
  });
  double price, size;
  Scanner scan = new Scanner(System.in);
  for(int i=0;i<MAX_NUM;++i){
   Screen screen = new Screen();
   size = scan.nextDouble();
   price = scan.nextDouble();
   screen.setSize(size);
   screen.setPrice(price);
   res.put(screen,i);
  }
  for(Screen screen:res.keySet()){
   screen.show();
  }
  return ;
 }
}
//  测试样例（输入）
//  1 2
//  3 4
//  5 6
//  7 8
//  9 10
//  1 2
//  3 4
//  3 4