Java code of Insertion sort

Introduction
Insertion sort is the best sorting algorithm for small-sized list of elements as compared to selection sort and bubble sort. This sorting algorithm always maintains a sorted sublist within an iteration i.e. it finds the correct position of a single element at a time and inserts it in its correct position within the currently sorted sublist.

Worst Complexity    : O(n*n)
Best Complexity       : O(n)
Average Complexity: O(n*n)


Imperative style using Java 7

public class InsertionSortExample {

 private static int array[] = {0,5,2,6,3,1,-9};
 
 public static void main(String[] args) {
  insertionSortAscending();
  System.out.println("Ascending Sorted List");
  for(int value : array) {
   System.out.print(value + " ");
  }
  
  insertionSortDescending();
  System.out.println("\nDescending Sorted List");
  for(int value : array) {
   System.out.print(value + " ");
  }
 }
 
 private static void insertionSortAscending() {
  //first element is considered as sorted sublist
  for(int outer=1; outer<array.length; outer++) {
   int temp = array[outer];
   int inner = outer-1;
   // array[inner] > temp is for ascending order
   while(inner >= 0 && array[inner] > temp) {
    array[inner+1] = array[inner];
    inner--;
   }
   array[inner+1] = temp;
  }
 }
 
 private static void insertionSortDescending() {
  for(int outer=1; outer<array.length; outer++) {
   int temp = array[outer];
   int inner = outer-1;
   // array[inner] < temp is for ascending order
   while(inner >= 0 && array[inner] < temp) {
    array[inner+1] = array[inner];
    inner--;
   }
   array[inner+1] = temp;
  }
 }
}




Declarative style using Java8

import java.util.Arrays;
import java.util.stream.IntStream;

public class InsertionSortJava8Example {

 private static int array[] = {0,5,2,6,3,1,-9};
 static int temp = 0;
 
 public static void main(String[] args) {
  insertionSortAscending();
  System.out.println("Ascending Sorted List");
  
  Arrays.stream(array).forEach(System.out::print);
  
  
  insertionSortDescending();
  System.out.println();
  System.out.println("Descending Sorted List");
  Arrays.stream(array).forEach(System.out::print);
 }
 
 private static void insertionSortAscending() {
  IntStream.range(1, array.length)
  .forEach(outer -> {
   int temp = array[outer];
   int inner = outer-1;
   // array[inner] > temp is for ascending order
   while(inner >= 0 && array[inner] > temp) {
    array[inner+1] = array[inner];
    inner--;
   }
   array[inner+1] = temp;
  });
 }
 
 private static void insertionSortDescending() {  
  IntStream.range(1, array.length)
  .forEach(outer -> {
   int temp = array[outer];
   int inner = outer-1;
   // array[inner] < temp is for ascending order
   while(inner >= 0 && array[inner] < temp) {
    array[inner+1] = array[inner];
    inner--;
   }
   array[inner+1] = temp;
  });
 }
}

Input   :  0,5,2,6,3,1,-9
Output: -9 0 1 2 3 5 6 (Ascending)
Output: 6 5 3 2 1 0 -9 (Descending)

Conclusion
In this post, we learned the implementation of insertion sort in Java language. Please leave your comments in the comments box. Thank you.