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Sorting Java List using Collections.sort()
Using Collections.sort() with Natural Order:
The Collections.sort() method sorts the list in the natural order. This is the simplest way to sort a list of comparable elements.
import java.util.*;
class Example {
public static void main(String args[]) {
List list = new ArrayList();
list.add("Banana");
list.add("Apple");
list.add("Cherry");
Collections.sort(list);
System.out.println(list);
}
}
Console Output:
[Apple, Banana, Cherry]
Sorting Java List using Comparator
Using Comparator for Custom Order:
A Comparator can be used for custom sorting logic. For example, sorting strings by length.
import java.util.*;
class Example {
public static void main(String args[]) {
List list = new ArrayList();
list.add("Banana");
list.add("Apple");
list.add("Cherry");
Collections.sort(list, new Comparator() {
public int compare(String s1, String s2) {
return s1.length() - s2.length();
}
});
System.out.println(list);
}
}
Console Output:
[Apple, Banana, Cherry]
Sorting Java List of Integers
Sorting Integers in Ascending Order:
Using Collections.sort() to sort integers in ascending order.
import java.util.*;
class Example {
public static void main(String args[]) {
List list = new ArrayList();
list.add(3);
list.add(1);
list.add(2);
Collections.sort(list);
System.out.println(list);
}
}
Console Output:
[1, 2, 3]
Sorting Java List using Lambda Expression
Using Lambda for Custom Sorting:
Lambda expressions can simplify the syntax when implementing a Comparator for custom sorting.
import java.util.*;
class Example {
public static void main(String args[]) {
List list = new ArrayList();
list.add("Banana");
list.add("Apple");
list.add("Cherry");
Collections.sort(list, (s1, s2) -> s2.compareTo(s1));
System.out.println(list);
}
}
Console Output:
[Cherry, Banana, Apple]
Sorting Java List of Custom Objects
Sorting Custom Objects by Property:
Use Comparator to sort a list of custom objects by a specific property.
import java.util.*;
class Person {
String name;
int age;
Person(String name, int age) {
this.name = name;
this.age = age;
}
public String toString() {
return name + ":" + age;
}
}
class Example {
public static void main(String args[]) {
List list = new ArrayList();
list.add(new Person("Alice", 30));
list.add(new Person("Bob", 25));
list.add(new Person("Charlie", 35));
Collections.sort(list, (p1, p2) -> p1.age - p2.age);
System.out.println(list);
}
}
Console Output:
[Bob:25, Alice:30, Charlie:35]
Sorting Java List in Reverse Order
Using Collections.reverseOrder():
The Collections.reverseOrder() method can be used to sort a list in reverse order.
import java.util.*;
class Example {
public static void main(String args[]) {
List list = new ArrayList();
list.add(3);
list.add(1);
list.add(2);
Collections.sort(list, Collections.reverseOrder());
System.out.println(list);
}
}
Console Output:
[3, 2, 1]
Sorting Java List with Stream API
Using Stream.sorted():
Java 8 Stream API provides a sorted() method to sort a list in a functional style.
import java.util.*;
import java.util.stream.*;
class Example {
public static void main(String args[]) {
List list = Arrays.asList("Banana", "Apple", "Cherry");
List sortedList = list.stream().sorted().collect(Collectors.toList());
System.out.println(sortedList);
}
}
Console Output:
[Apple, Banana, Cherry]
Sorting Java List with Multiple Criteria
Sorting by Multiple Criteria:
Use Comparator.thenComparing() to sort by multiple criteria, such as sorting by name and then by age.
import java.util.*;
class Person {
String name;
int age;
Person(String name, int age) {
this.name = name;
this.age = age;
}
public String toString() {
return name + ":" + age;
}
}
class Example {
public static void main(String args[]) {
List list = new ArrayList();
list.add(new Person("Alice", 30));
list.add(new Person("Bob", 25));
list.add(new Person("Alice", 25));
Collections.sort(list, Comparator.comparing(Person::getName).thenComparing(Person::getAge));
System.out.println(list);
}
}
Console Output:
[Alice:25, Alice:30, Bob:25]
Sorting Java List with Natural Order and Nulls First
Sorting with Null Values:
Use Comparator.nullsFirst() to handle null values while sorting.
import java.util.*;
class Example {
public static void main(String args[]) {
List list = Arrays.asList("Banana", null, "Cherry", "Apple");
Collections.sort(list, Comparator.nullsFirst(Comparator.naturalOrder()));
System.out.println(list);
}
}
Console Output:
[null, Apple, Banana, Cherry]
