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///
通过ArrayList将map.entrySet()，变成list
然后在类外写具体如何比较大小的方法compare()，最后调用
Collections.sort(list, new Comparator<Map.Entry<String, String>>()
import java.util.*;
public class MapSort {
public static void main(String[] args) {
Map<String,String> map=new HashMap<>();
map.put("say","no");
map.put("hash","baby");
map.put("you","know");
System.out.println("排序前");
for (String s : map.keySet()) {
System.out.println(s+":"+map.get(s));
}
//通过ArrayList构造函数将map.entrySet()转换成list
List<Map.Entry<String,String>> list= new ArrayList<>(map.entrySet());
//通过比较器进行比较排序
Collections.sort(list, new Comparator<Map.Entry<String, String>>() {
@Override
public int compare(Map.Entry<String, String> entry1, Map.Entry<String, String> entry2) {
//返回值为1，代表前面>后面，-1相反，0表示相等
return entry1.getKey().compareTo(entry2.getKey());
}
});
//将排序后的结果打印出来
System.out.println("排序后:");
for (Map.Entry<String, String> entry : list) {
System.out.println(entry.getKey()+":"+entry.getValue());
}
}
}
///
import java.util.*;
public class value {
public static void main(String[] args) {
Map<String,String> map=new HashMap<>();
map.put("say","no");
map.put("hash","baby");
map.put("you","know"); System.out.println("排序前");
for (String s : map.keySet()) {
System.out.println(s+":"+map.get(s));
}
//通过ArrayList构造函数将map.entrySet()转换成list
List<Map.Entry<String,String>> list= new ArrayList<>(map.entrySet());
//通过比较器进行比较排序
Collections.sort(list, new Comparator<Map.Entry<String, String>>() {
@Override
public int compare(Map.Entry<String, String> entry1, Map.Entry<String, String> entry2) {
//返回值为1，代表前面>后面，-1相反，0表示相等
return entry1.getValue().compareTo(entry2.getValue());
}
});
//将排序后的结果打印出来
System.out.println("排序后");
for (Map.Entry<String, String> entry : list) {
System.out.println(entry.getKey()+":"+entry.getValue());
}
}
}
TreeMap的按值排序和上面那个基本一致且更常用。
TreeMap 的默认是按照key排序。
