Java Tutorials

Selection Sort Example Program in Java

Mallik4 Comments

package in.malliktalksjava;

/**
* @author malliktalksjava
* @version 1.0
*
* Below class sorts the given array using SelectionSort
* mechanism and prints the output into console.
*/
public class SelectionSortExample {

/**
* @param args
*/
public static void main(String args[]){

int[] arr1 = {12,434,2,23,7,44,66,42};
int[] arr2 = doSelectionSort(arr1);
for(int var:arr2){
System.out.print(var);
System.out.print(“, “);
}
}

/**
* @param arr
* @return sorted array
*/
public static int[] doSelectionSort(int[] arr){

for (int count = 0; count < arr.length – 1; count++)
{
int index = count;
for (int count2 = count + 1; count2 < arr.length; count2++){
if (arr[count2] < arr[index]){
index = count2;
}
}

int smallerNumber = arr[index];
arr[index] = arr[count];
arr[count] = smallerNumber;
}
return arr;
}
}

 

Other Useful Links:

Bubble Sort Example in JAVA

Insertion Sort Example program in JAVA

Quick Sort Example Program in Java

Merge Sort Example in Java

Bubble Sort Example in JAVA

Mallik4 Comments 

package in.malliktalksjava;

/**
* @author malliktalksjava
*
*/
public class BubbleSortExample {

private static int[] input = { 4, 2, 9, 6, 23, 11, 44, 0 };

public static void bubbleSort(int arr[]) {
 int count = array.length;
 int var;
 for (int i = count; i >= 0; i--) {
   for (int j = 0; j  array[j+1]) {
          swapNumbers(temp2, var, array);
      }
   }
 printNumbers(array);
 }
}

private static void swapNumbers(int var1, int var2, int[] array) {
   int temp = array[var1];
   array[var1] = array[var2];
   array[var2] = temp;
}

private static void printNumbers(int[] input) {
  for (int i = 0; i < input.length; i++) {
    System.out.println(input[i] + ", ");
  }
}
}

Other Useful Links:

Selection Sort Example Program in JAVA

Insertion Sort Example program in JAVA

Quick Sort Example Program in Java

Merge Sort Example in Java

Number series example program using JAVA

MallikLeave a comment

package in.malliktalksjava;

/**
* @author malliktalksjava.in
*
* This program prints the numbers in below pattern
* 1
* 123
* 12345
* 1234567
* 12345
* 123
* 1
*/
class PrintingNumberPatterns{

public static void main(String[] args){
printNumberSeries();
}

/**
* Print the numbers in assending and decending order by iterating it.
*/
private static void printNumberSeries() {
for (int i = 1; i <= 7; i += 2) {
for (int j = 1; j <= i; j++) {
System.out.print(j);
}
System.out.println();
}

for (int i = 5; i >= 1; i -= 2) {
for (int j = 1; j < i + 1; j++) {
System.out.print(j);
}
System.out.println();
}
}
}

Example program to reverse a Number in Java

Mallik2 Comments

 

package in.javatutorials;

public class ReverseNumber {

public static void main(String[] args) {
System.out.println(“The reversed number is ” + reverse(1234));
}

public static int reverse(int input) {
int result = 0;
int rem;
while (input > 0) {
rem = input % 10;
input = input / 10;
result = result * 10 + rem;
}
return result;
}
}

 

Avoid nested loops using Collection Framework in Java

Mallik2 Comments

High performance is essential for any software implemented in any programming language. And, loops plays major role in this regard. This post explains how to avoid the loops using Java’s Collection framework.

Below are the two Java programs to understand how the performance could be increased using the Collection framework.

Using nested loops

package in.javatutorials;

/**
* Finds out the Duplicates is String Array using Nested Loops.
*/
public class UsingNesteadLoops {
  private static String[] strArray = { "Cat", "Dog", "Tiger",     "Lion", "Lion" };

  public static void main(String[] args) {
   isThereDuplicateUsingLoops(strArray);
  }

  /**
   * Iterates the String array and finds out the duplicates 
   */
   public static void isThereDuplicateUsingLoops(String[]     strArray) {

   boolean duplicateFound = false;
   int loopCounter = 0;

   for (int i = 0; i < strArray.length; i++) {
   String str = strArray[i];
   int countDuplicate = 0;

   for (int j = 0; j < strArray.length; j++) {
      String str2 = strArray[j];
      if (str.equalsIgnoreCase(str2)) {
         countDuplicate++;
      }
      if (countDuplicate > 1) {
         duplicateFound = true;
         System.out.println("Duplicates Found for " + str);
      }
      loopCounter++;
   }// end of inner nested for loop

   if (duplicateFound) {
    break;
   }
}// end of outer for loop

System.out.println("Looped " + loopCounter + " times to find the result");
}

}

If we run the above program, it will be looped 20 times to find out the duplicates in the string array which has the length of 5. Number of loops increases exponentially depending on size of array, hence the performance takes a hit. These are not acceptable to use in applications which require high performance.

Without using nested loops

package in.javatutorials;

import java.util.HashSet;
import java.util.Set;

/**
* Finds out the Duplicates is String Array using Collection.
*/
public class AvoidNesteadLoopsUsingCollections {

private static String[] strArray = { "Cat", "Dog", "Tiger", "Lion", "Lion" };

public static void main(String[] args) {
 isThereDuplicateUsingSet(strArray);
}

/**
* Iterates the String array and finds out the duplicates
*/
public static void isThereDuplicateUsingSet(String[] strArray) {
  boolean duplicateFound = false;
  int loopCounter = 0;
  Set setValues = new HashSet();

  for (int i = 0; i < strArray.length; i++) {
    String str = strArray[i];

    if(setValues.contains(str)){
        duplicateFound = true;
        System.out.println("Duplicates Found for " + str);
    }
    setValues.add(str);
    loopCounter++;

    if (duplicateFound) {
       break;
    }
   }// end of for loop

   System.out.println("Looped " + loopCounter + " times to find the result");
 }

}
  • Above approach takes only 5 loops to identify the duplicates in the same array.
  • It is more readable , easier to maintain and performs better.
  • If you have an array with 1000 items, then nested loops will loop through 999000 times and utilizing a collection will loop through only 1000 times.

Other Useful links: