# Sorting a Hashmap according to values

Hello Everyone,

Given marks scored out of 100 by a student in subjects where the name of the subject is key and marks scored is the value. Our task is to sort the hashmap according to values i.e. according to marks.
Example:

Input : Key = Math, Value = 98 Key = Data Structure, Value = 85 Key = Database, Value = 91 Key = Java, Value = 95 Key = Operating System, Value = 79 Key = Networking, Value = 80 Output : Key = Operating System, Value = 79 Key = Networking, Value = 80 Key = Data Structure, Value = 85 Key = Database, Value = 91 Key = Java, Value = 95 Key = Math, Value = 98

Solution: The idea is to store the entry set in a list and sort the list on the basis of values. Then fetch values and keys from the list and put them in a new hashmap. Thus, a new hashmap is sorted according to values.
Below is the implementation of the above idea:

• Java

`// Java program to sort hashmap by values`

`import` `java.util.*;`

`import` `java.lang.*;`

`public` `class` `GFG {`

` ` `// function to sort hashmap by values`

` ` `public` `static` `HashMap<String, Integer> sortByValue(HashMap<String, Integer> hm)`

` ` `{`

` ` `// Create a list from elements of HashMap`

` ` `List<Map.Entry<String, Integer> > list =`

` ` `new` `LinkedList<Map.Entry<String, Integer> >(hm.entrySet());`

` ` `// Sort the list`

` ` `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());`

` ` `}`

` ` `});`

` `

` ` `// put data from sorted list to hashmap`

` ` `HashMap<String, Integer> temp = ` `new` `LinkedHashMap<String, Integer>();`

` ` `for` `(Map.Entry<String, Integer> aa : list) {`

` ` `temp.put(aa.getKey(), aa.getValue());`

` ` `}`

` ` `return` `temp;`

` ` `}`

` ` `// Driver Code`

` ` `public` `static` `void` `main(String[] args)`

` ` `{`

` ` `HashMap<String, Integer> hm = ` `new` `HashMap<String, Integer>();`

` ` `// enter data into hashmap`

` ` `hm.put(` `"Math"` `, ` `98` `);`

` ` `hm.put(` `"Data Structure"` `, ` `85` `);`

` ` `hm.put(` `"Database"` `, ` `91` `);`

` ` `hm.put(` `"Java"` `, ` `95` `);`

` ` `hm.put(` `"Operating System"` `, ` `79` `);`

` ` `hm.put(` `"Networking"` `, ` `80` `);`

` ` `Map<String, Integer> hm1 = sortByValue(hm);`

` ` `// print the sorted hashmap`

` ` `for` `(Map.Entry<String, Integer> en : hm1.entrySet()) {`

` ` `System.out.println(` `"Key = "` `+ en.getKey() +`

` ` `", Value = "` `+ en.getValue());`

` ` `}`

` ` `}`

`}`

Output

Key = Operating System, Value = 79 Key = Networking, Value = 80 Key = Data Structure, Value = 85 Key = Database, Value = 91 Key = Java, Value = 95 Key = Math, Value = 98

Using Java 8 Lambdas

Here we will change how we did sorting and will use lambda expression for sorting. The logic is the same, and even we also passed the comparator object but only using lambda.

Below is the implementation of the above approach:

• Java

`// Java program to sort hashmap by values`

`import` `java.lang.*;`

`import` `java.util.*;`

`public` `class` `GFG {`

` ` `// function to sort hashmap by values`

` ` `public` `static` `HashMap<String, Integer>`

` ` `sortByValue(HashMap<String, Integer> hm)`

` ` `{`

` ` `// Create a list from elements of HashMap`

` ` `List<Map.Entry<String, Integer> > list`

` ` `= ` `new` `LinkedList<Map.Entry<String, Integer> >(`

` ` `hm.entrySet());`

` ` `// Sort the list using lambda expression`

` ` `Collections.sort(`

` ` `list,`

` ` `(i1,`

` ` `i2) -> i1.getValue().compareTo(i2.getValue()));`

` ` `// put data from sorted list to hashmap`

` ` `HashMap<String, Integer> temp`

` ` `= ` `new` `LinkedHashMap<String, Integer>();`

` ` `for` `(Map.Entry<String, Integer> aa : list) {`

` ` `temp.put(aa.getKey(), aa.getValue());`

` ` `}`

` ` `return` `temp;`

` ` `}`

` ` `// Driver Code`

` ` `public` `static` `void` `main(String[] args)`

` ` `{`

` ` `HashMap<String, Integer> hm`

` ` `= ` `new` `HashMap<String, Integer>();`

` ` `// enter data into hashmap`

` ` `hm.put(` `"Math"` `, ` `98` `);`

` ` `hm.put(` `"Data Structure"` `, ` `85` `);`

` ` `hm.put(` `"Database"` `, ` `91` `);`

` ` `hm.put(` `"Java"` `, ` `95` `);`

` ` `hm.put(` `"Operating System"` `, ` `79` `);`

` ` `hm.put(` `"Networking"` `, ` `80` `);`

` ` `Map<String, Integer> hm1 = sortByValue(hm);`

` ` `// print the sorted hashmap`

` ` `for` `(Map.Entry<String, Integer> en :`

` ` `hm1.entrySet()) {`

` ` `System.out.println(` `"Key = "` `+ en.getKey()`

` ` `+ ` `", Value = "`

` ` `+ en.getValue());`

` ` `}`

` ` `}`

`}`

Output

Key = Operating System, Value = 79 Key = Networking, Value = 80 Key = Data Structure, Value = 85 Key = Database, Value = 91 Key = Java, Value = 95 Key = Math, Value = 98