Java Bubble Sort Example

/*
 Java Bubble Sort Example
 This Java bubble sort example shows how to sort an array of int using bubble 
 sort algorithm. Bubble sort is the simplest sorting algorithm.
*/
 
public class BubbleSort {
 
 public static void main(String[] args) {
 
  //create an int array we want to sort using bubble sort algorithm
  int intArray[] = new int[]{5,90,35,45,150,3};
 
  //print array before sorting using bubble sort algorithm
  System.out.println("Array Before Bubble Sort");
  for(int i=0; i < intArray.length; i++){
   System.out.print(intArray[i] + " ");
  }
 
  //sort an array using bubble sort algorithm
  bubbleSort(intArray);
 
  System.out.println("");
 
  //print array after sorting using bubble sort algorithm
  System.out.println("Array After Bubble Sort");
  for(int i=0; i < intArray.length; i++){
   System.out.print(intArray[i] + " ");
  }
 
 }
 
 private static void bubbleSort(int[] intArray) {
 
  /*
   * In bubble sort, we basically traverse the array from first 
   * to array_length - 1 position and compare the element with the next one. 
   * Element is swapped with the next element if the next element is greater.
   * 
   * Bubble sort steps are as follows.
   * 
   * 1. Compare array[0] & array[1]
   * 2. If array[0] > array [1] swap it.
   * 3. Compare array[1] & array[2]
   * 4. If array[1] > array[2] swap it.
   * ...
   * 5. Compare array[n-1] & array[n]
   * 6. if [n-1] > array[n] then swap it.
   * 
   * After this step we will have largest element at the last index.
   * 
   * Repeat the same steps for array[1] to array[n-1]
   *  
   */
 
  int n = intArray.length;
  int temp = 0;
 
  for(int i=0; i < n; i++){
   for(int j=1; j < (n-i); j++){
 
    if(intArray[j-1] > intArray[j]){
     //swap the elements!
     temp = intArray[j-1];
     intArray[j-1] = intArray[j];
     intArray[j] = temp;
    }
 
   }
  }
 
 }
}
 
/*
Output of the Bubble Sort Example would be
 
Array Before Bubble Sort
5 90 35 45 150 3 
Array After Bubble Sort
3 5 35 45 90 150
 
*/

Java Bubble Sort Descending Order

1. /*
2. Java Bubble Sort Descending Order Example
3. This Java bubble sort example shows how to sort an array of int in descending
4. order using bubble sort algorithm.
5. */
6.  
7. public class BubbleSortDescendingOrder {
8.  
9. public static void main(String[] args) {
10.  
11. //create an int array we want to sort using bubble sort algorithm
12. int intArray[] = new int[]{5,90,35,45,150,3};
13.  
14. //print array before sorting using bubble sort algorithm
15. System.out.println("Array Before Bubble Sort");
16. for(int i=0; i < intArray.length; i++){
17. System.out.print(intArray[i] + " ");
18. }
19.  
20. //sort an array in descending order using bubble sort algorithm
21. bubbleSort(intArray);
22.  
23. System.out.println("");
24.  
25. //print array after sorting using bubble sort algorithm
26. System.out.println("Array After Bubble Sort");
27. for(int i=0; i < intArray.length; i++){
28. System.out.print(intArray[i] + " ");
29. }
30.  
31. }
32.  
33. private static void bubbleSort(int[] intArray) {
34.  
35. /*
36. * In bubble sort, we basically traverse the array from first
37. * to array_length - 1 position and compare the element with the next one.
38. * Element is swapped with the next element if the next element is smaller.
39. *
40. * Bubble sort steps are as follows.
41. *
42. * 1. Compare array[0] & array[1]
43. * 2. If array[0] < array [1] swap it.
44. * 3. Compare array[1] & array[2]
45. * 4. If array[1] < array[2] swap it.
46. * ...
47. * 5. Compare array[n-1] & array[n]
48. * 6. if [n-1] < array[n] then swap it.
49. *
50. * After this step we will have smallest element at the last index.
51. *
52. * Repeat the same steps for array[1] to array[n-1]
53. *
54. */
55.  
56. int n = intArray.length;
57. int temp = 0;
58.  
59. for(int i=0; i < n; i++){
60. for(int j=1; j < (n-i); j++){
61.  
62. if(intArray[j-1] < intArray[j]){
63. //swap the elements!
64. temp = intArray[j-1];
65. intArray[j-1] = intArray[j];
66. intArray[j] = temp;
67. }
68.  
69. }
70. }
71.  
72. }
73. }
74.  
75. /*
76. Output of the Bubble Sort Descending Order Example would be
77.  
78. Array Before Bubble Sort
79. 5 90 35 45 150 3
80. Array After Bubble Sort
81. 150 90 45 35 5 3
82.  
83. */

For Loop

For loop executes group of Java statements as long as the boolean condition evaluates to true.

For loop combines three elements which we generally use: initialization statement, boolean expression and increment or decrement statement.

For loop syntax

for( <initialization> ; <condition> ; <statement> ){

<Block of statements>;

}

The initialization statement is executed before the loop starts. It is generally used to initialize the loop variable.

Condition statement is evaluated before each time the block of statements are executed. Block of statements are executed only if the boolean condition evaluates to true.

Statement is executed after the loop body is done. Generally it is being used to increment or decrement the loop variable.

Following example shows use of simple for loop.

for(int i=0 ; i < 5 ; i++)
{
System.out.println(“i is : “ + i);
}

It is possible to initialize multiple variable in the initialization block of the for loop by separating it by comma as given in the below example.

for(int i=0, j =5 ; i < 5 ; i++)

It is also possible to have more than one increment or decrement section as well as given below.

for(int i=0; i < 5 ; i++, j--)

However it is not possible to include declaration and initialization in the initialization block of the for loop.

Also, having multiple conditions separated by comma also generates the compiler error. However, we can include multiple condition with && and || logical operators.

Declare multiple variables in for loop Example

/*
  Declare multiple variables in for loop Example
  This Java Example shows how to declare multiple variables in Java For loop using
  declaration block.
*/
 
public class DeclaringMultipleVariablesInForLoopExample {
 
  public static void main(String[] args) {
 
    /*
     * Multiple variables can be declared in declaration block of for loop.
     */
 
     for(int i=0, j=1, k=2 ; i<5 ; i++)
       System.out.println("I : " + i + ",j : "+ j + ", k : " + k);
 
     /*
      * Please note that the variables which are declared, should be of same type
      * as in this example int.
      */  
 
      //THIS WILL NOT COMPILE
      //for(int i=0, float j; i < 5; i++);
  }
}