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java-comparator-in-hashmap/build.gradle

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+plugins {
+ id 'java-library'
+}
+
+sourceCompatibility = 12
+targetCompatibility = 12
+
+repositories {
+ jcenter()
+}
+
+dependencies {
+}

java-comparator-in-hashmap/readme.rst

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+You can read tutorial https://www.roytuts.com/using-comparator-in-hashmap/

java-comparator-in-hashmap/src/main/java/com/roytuts/java/comparator/in/hashmap/Book.java

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+package com.roytuts.java.comparator.in.hashmap;
+
+public class Book {
+
+ private String title;
+ private String author;
+
+ public Book(String title, String author) {
+ this.title = title;
+ this.author = author;
+ }
+
+ public String getTitle() {
+ return title;
+ }
+
+ public String getAuthor() {
+ return author;
+ }
+
+ @Override
+ public int hashCode() {
+ final int prime = 31;
+ int result = 1;
+ result = prime * result + ((author == null) ? 0 : author.hashCode());
+ result = prime * result + ((title == null) ? 0 : title.hashCode());
+ return result;
+ }
+
+ @Override
+ public boolean equals(Object obj) {
+ if (this == obj)
+ return true;
+ if (obj == null)
+ return false;
+ if (getClass() != obj.getClass())
+ return false;
+ Book other = (Book) obj;
+ if (author == null) {
+ if (other.author != null)
+ return false;
+ } else if (!author.equals(other.author))
+ return false;
+ if (title == null) {
+ if (other.title != null)
+ return false;
+ } else if (!title.equals(other.title))
+ return false;
+ return true;
+ }
+
+ @Override
+ public String toString() {
+ return "Book [title=" + title + ", author=" + author + "]";
+ }
+
+}

java-comparator-in-hashmap/src/main/java/com/roytuts/java/comparator/in/hashmap/HashMapComparator.java

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+package com.roytuts.java.comparator.in.hashmap;
+
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.Comparator;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.Map.Entry;
+import java.util.Set;
+
+public class HashMapComparator {
+
+ public static void main(String[] args) {
+ Map<Book, String> bookMap = new HashMap<>();
+
+ bookMap.put(new Book("Java", "James Gosling"), "Java");
+ bookMap.put(new Book("C++", "Bjourn Stroustup"), "C++");
+ bookMap.put(new Book("C", "Denish Ritche"), "C");
+ bookMap.put(new Book("Databse", "C J Date"), "Database");
+
+ System.out.println("Unsorted HashMap Values");
+ System.out.println("-----------------------");
+
+ bookMap.forEach((k, v) -> System.out.println(k + " => " + v));
+
+ System.out.println();
+
+ Set<Entry<Book, String>> set = bookMap.entrySet();
+ List<Entry<Book, String>> list = new ArrayList<Entry<Book, String>>(set);
+
+ //Collections.sort(list, (b1, b2) -> (b1.getValue()).compareTo(b2.getValue()));
+
+ Collections.sort(list, new Comparator<Map.Entry<Book, String>>() {
+ @Override
+ public int compare(Entry<Book, String> b1, Entry<Book, String> b2) {
+ return (b1.getValue()).compareTo(b2.getValue());
+ }
+ });
+
+ System.out.println("Sorted HashMap Values");
+ System.out.println("---------------------");
+
+ list.forEach(item -> System.out.println(item.getKey() + " => " + item.getValue()));
+ }
+
+}