8000 Java 8 Comparator Comparing Reverse Order · TGAMendis/CoreJava@7dd5153 · GitHub
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JavaProgramTo.com
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Java 8 Comparator Comparing Reverse Order
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9 files changed

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‎src/main/java/com/javaprogramto/java8/comparator/reverse/ComparatorReverse.java

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package com.javaprogramto.java8.comparator.reverse;
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import java.util.Arrays;
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import java.util.Collections;
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import java.util.List;
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public class ComparatorReverse {
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public static void main(String[] args) {
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List<String> list = Arrays.asList("1", "3", "2");
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System.out.println("Original list - " + list);
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Collections.reverse(list);
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System.out.println("Reversed list - " + list);
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}
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}

‎src/main/java/com/javaprogramto/java8/comparator/reverse/ComparatorReverse2.java

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package com.javaprogramto.java8.comparator.reverse;
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import java.util.Arrays;
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import java.util.Comparator;
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import java.util.List;
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import java.util.stream.Collectors;
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public class ComparatorReverse2 {
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public static void main(String[] args) {
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List<String> list = Arrays.asList("1", "3", "2");
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System.out.println("Original list - " + list);
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List<String> sortedList = list.stream().sorted(Comparator.reverseOrder()).collect(Collectors.toList());
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System.out.println("Sorted list - " + sortedList);
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}
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}

‎src/main/java/com/javaprogramto/java8/comparator/reverse/ComparatorReverse3.java

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package com.javaprogramto.java8.comparator.reverse;
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import java.util.Arrays;
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import java.util.Comparator;
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import java.util.List;
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import java.util.stream.Collectors;
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public class ComparatorReverse3 {
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public static void main(String[] args) {
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List<String> list = Arrays.asList("1", "3", "2");
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System.out.println("Original list - " + list);
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List<String> result1 = list.stream().sorted(Comparator.reverseOrder()).collect(Collectors.toList());
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System.out.println("result 1 " + result1);
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List<String> result2 = result1.stream().sorted(Comparator.reverseOrder()).collect(Collectors.toList());
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System.out.println("result 2 - " + result2);
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}
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}

‎src/main/java/com/javaprogramto/java8/comparator/reverse/ComparatorReverse4.java

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package com.javaprogramto.java8.comparator.reverse;
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import java.util.Arrays;
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import java.util.Comparator;
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import java.util.List;
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import java.util.stream.Collectors;
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public class ComparatorReverse4 {
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public static void main(String[] args) {
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List<String> list = Arrays.asList("100", "3", "20");
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System.out.println("Original list - " + list);
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Comparator<String> sortByLength = Comparator.comparing(String::length);
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List<String> sortedList = list.stream().sorted(sortByLength).collect(Collectors.toList());
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System.out.println("Sorted by length ascending order - " + sortedList);
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Comparator<String> sortByLengthReverse = sortByLength.reversed();
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sortedList = list.stream().sorted(sortByLengthReverse).collect(Collectors.toList());
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System.out.println("Sorted by length descending order - " + sortedList);
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}
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}

‎src/main/java/com/javaprogramto/java8/comparator/reverse/ComparatorReverse5.java

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package com.javaprogramto.java8.comparator.reverse;
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import java.util.ArrayList;
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import java.util.Comparator;
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import java.util.List;
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import java.util.stream.Collectors;
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public class ComparatorReverse5 {
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public static void main(String[] args) {
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List<Teacher> teachers = new ArrayList<>();
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teachers.add(new Teacher("Rajesh", "Science", 10));
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teachers.add(new Teacher("Mahesh", "Mathematics", 5));
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teachers.add(new Teacher("Suresh", "English", 10));
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teachers.add(new Teacher("Rakesh", "Science", 3));
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teachers.add(new Teacher("Ramesh", "Mathematics", 8));
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System.out.println("Original teachers list - ");
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teachers.forEach(t -> System.out.println(t.getName()));
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Comparator<Teacher> sortByName = (t1, t2) -> t1.getName().compareTo(t2.getName());
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List<Teacher> sortBynameList = teachers.stream().sorted(sortByName).collect(Collectors.toList());
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System.out.println("\nSorted by name ascending order");
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sortBynameList.forEach(t -> System.out.println(t.getName()));
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Comparator<Teacher> sortByNameReverse = sortByName.reversed();
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sortBynameList = teachers.stream().sorted(sortByNameReverse).collect(Collectors.toList());
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System.out.println("Sorted by name descending order ");
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sortBynameList.forEach(t -> System.out.println(t.getName()));
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}
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}

‎src/main/java/com/javaprogramto/java8/comparator/reverse/ComparatorReverse6.java

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package com.javaprogramto.java8.comparator.reverse;
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import java.util.ArrayList;
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import java.util.Comparator;
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import java.util.List;
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import java.util.stream.Collectors;
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public class ComparatorReverse6 {
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public static void main(String[] args) {
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List<Teacher2> Teacher2s = new ArrayList<>();
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Teacher2s.add(new Teacher2("Rajesh", "Science", 10));
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Teacher2s.add(new Teacher2("Mahesh", "Mathematics", 5));
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Teacher2s.add(new Teacher2("Suresh", "English", 10));
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Teacher2s.add(new Teacher2("Rakesh", "Science", 3));
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Teacher2s.add(new Teacher2("Ramesh", "Mathematics", 8));
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System.out.println("Original Teacher2s list - ");
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Teacher2s.forEach(t -> System.out.println(t.getSubject()));
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List<Teacher2> sortBynameList = Teacher2s.stream().sorted()
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.collect(Collectors.toList());
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System.out.println("\nSorted by subject ascending order");
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sortBynameList.forEach(t -> System.out.println(t.getSubject()));
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sortBynameList = Teacher2s.stream().sorted(Comparator.reverseOrder()).collect(Collectors.toList());
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System.out.println("\nSorted by subject descending order ");
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sortBynameList.forEach(t -> System.out.println(t.getSubject()));
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}
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}

‎src/main/java/com/javaprogramto/java8/comparator/reverse/Teacher.java

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package com.javaprogramto.java8.comparator.reverse;
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public class Teacher {
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String name;
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String subject;
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int experience;
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public Teacher(String name, String subject, int experience) {
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super();
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this.name = name;
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this.subject = subject;
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this.experience = experience;
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}
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public String getName() {
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return name;
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}
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public void setName(String name) {
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this.name = name;
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}
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public String getSubject() {
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return subject;
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}
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public void setSubject(String subject) {
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this.subject = subject;
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}
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public int getExperience() {
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return experience;
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}
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public void setExperience(int experience) {
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this.experience = experience;
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}
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}

‎src/main/java/com/javaprogramto/java8/comparator/reverse/Teacher2.java

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package com.javaprogramto.java8.comparator.reverse;
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public class Teacher2 implements Comparable<Teacher2>{
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String name;
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String subject;
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int experience;
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public Teacher2(String name, String subject, int experience) {
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super();
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this.name = name;
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this.subject = subject;
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this.experience = experience;
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}
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public String getName() {
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return name;
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}
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public void setName(String name) {
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this.name = name;
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}
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public String getSubject() {
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return subject;
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}
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public void setSubject(String subject) {
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this.subject = subject;
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}
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public int getExperience() {
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return experience;
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}
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public void setExperience(int experience) {
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this.experience = experience;
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}
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@Override
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public int compareTo(Teacher2 o) {
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// TODO Auto-generated method stub
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return this.getSubject().compareTo(o.getSubject());
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}
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}

‎src/main/java/com/javaprogramto/java8/comparator/thencomparing/SortByThreeFieldsByThenComparing.java

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Comparator<Author> lastNameComparator = Comparator.comparing(Author::getLastName);
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// thenComparing() method to merge 3 comparators in chain.
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Comparator<Author> firstMiddleNamesComparator = firstNameComparator.thenComparing(middleNameComparator)
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Comparator<Author> fullNamesComparator = firstNameComparator.thenComparing(middleNameComparator)
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.thenComparing(lastNameComparator);
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System.out.println("Before sorting by 3 fields");
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authors.forEach(a -> System.out.println(a));
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Collections.sort(authors, firstMiddleNamesComparator);
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Collections.sort(authors, fullNamesComparator);
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authors.sort(fullNamesComparator);
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System.out.println("after sorting merged comparator");
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authors.forEach(a -> System.out.println(a));

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