极客笔记Java 按值排序Map
在本文中，我们将了解如何按值对Map进行排序。Java HashMap是Java的Map接口的基于哈希表的实现。它是key-value对的集合。
以下是同样的示例 −
假设我们的输入是 −
Input HashMap:
Key = Java, Value = 45
Key = Scala, Value = 20
Key = Mysql, Value = 11
Key = Python, Value = 75
期望的输出将是 −
The HashMap after sorting is:
Key = Mysql, Value = 11
Key = Scala, Value = 20
Key = Java, Value = 45
Key = Python, Value = 75
步骤
Step 1 - START
Step 2 - Declare namely
Step 3 - Define the values.
Step 4 - Use the ‘sort’ method to sort the elements of the map.
Step 5 - Use the ‘getValue’ method to fetch the values and use the ‘compareTo’ method to comare two values.
Step 6 - Iterate through the hashmap, and use the ‘getKey’ method to fetch the values into ‘temp’. Use ‘temp’ as the return value.
Step 7 - Display the result
Step 8 - Stop
示例1
在这里，我们将所有的操作都绑定在“main”函数下。
import java.util.*;
import java.lang.*;
public class Demo {
public static HashMap<String, Integer> sort(HashMap<String, Integer> input_map){
List<Map.Entry<String, Integer> > list =
new LinkedList<Map.Entry<String, Integer> >(input_map.entrySet());
Collections.sort(list, new Comparator<Map.Entry<String, Integer> >() {
public int compare(Map.Entry<String, Integer> o1,
Map.Entry<String, Integer> o2){
return (o1.getValue()).compareTo(o2.getValue());
}
});
HashMap<String, Integer> temp = new LinkedHashMap<String, Integer>();
for (Map.Entry<String, Integer> aa : list) {
temp.put(aa.getKey(), aa.getValue());
}
return temp;
}
public static void main(String[] args){
HashMap<String, Integer> input_map = new HashMap<String, Integer>();
input_map.put("Java", 45);
input_map.put("Scala", 20);
input_map.put("Mysql", 11);
input_map.put("Python", 75);
System.out.println("The HashMap is defined as:");
for (Map.Entry<String, Integer> element : input_map.entrySet()) {
System.out.println("Key = " + element.getKey() + ", Value = " + element.getValue());
}
Map<String, Integer> result_map = sort(input_map);
System.out.println("\nThe HashMap after sorting is:");
for (Map.Entry<String, Integer> element : result_map.entrySet()) {
System.out.println("Key = " + element.getKey() + ", Value = " + element.getValue());
}
}
}
输出
The HashMap is defined as:
Key = Java, Value = 45
Key = Scala, Value = 20
Key = Mysql, Value = 11
Key = Python, Value = 75
The HashMap after sorting is:
Key = Mysql, Value = 11
Key = Scala, Value = 20
Key = Java, Value = 45
Key = Python, Value = 75
示例2
在这里，我们将操作封装到展示面向对象编程的函数中。
import java.util.*;
import java.lang.*;
public class Demo {
public static void main(String[] args){
HashMap<String, Integer> input_map = new HashMap<String, Integer>();
input_map.put("Java", 45);
input_map.put("Scala", 20);
input_map.put("Mysql", 11);
input_map.put("Python", 75);
System.out.println("The HashMap is defined as:");
for (Map.Entry<String, Integer> element : input_map.entrySet()) {
System.out.println("Key = " + element.getKey() + ", Value = " + element.getValue());
}
List<Map.Entry<String, Integer> > list =
new LinkedList<Map.Entry<String, Integer> >(input_map.entrySet());
Collections.sort(list, new Comparator<Map.Entry<String, Integer> >() {
public int compare(Map.Entry<String, Integer> o1,
Map.Entry<String, Integer> o2){
return (o1.getValue()).compareTo(o2.getValue());
}
});
HashMap<String, Integer> result_map = new LinkedHashMap<String, Integer>();
for (Map.Entry<String, Integer> aa : list) {
result_map.put(aa.getKey(), aa.getValue());
}
System.out.println("\nThe HashMap after sorting is:");
for (Map.Entry<String, Integer> element : result_map.entrySet()) {
System.out.println("Key = " + element.getKey() + ", Value = " + element.getValue());
}
}
}
输出
The HashMap is defined as:
Key = Java, Value = 45
Key = Scala, Value = 20
Key = Mysql, Value = 11
Key = Python, Value = 75
The HashMap after sorting is:
Key = Mysql, Value = 11
Key = Scala, Value = 20
Key = Java, Value = 45
Key = Python, Value = 75