Reverse String Array Example

1. /*
           Java Reverse String Array Example
           This Java Reverse String Array example shows how to find sort an array of
           String in Java using Arrays and Collections classes.
    */
   
   
   import java.util.Collections;
   import java.util.List;
   import java.util.Arrays;
   
   
   public class ReverseStringArrayExample {
   
   
           public static void main(String args[]){
   
   
                   //String array
                   String[] strDays = new String[]{“Sunday”, “Monday”, “Tuesday”, “Wednesday”};
   
   
                   /*
                    * There are basically two methods, one is to use temporary array and
                    * manually loop through the elements of an Array and swap them or to use
                    * Arrays and Collections classes.
                    *
                    * This example uses the second approach i.e. without temp variable.
                    *
                    */
                  
                   //first create a list from String array
                   List<String> list = Arrays.asList(strDays);
   
   
                   //next, reverse the list using Collections.reverse method
                   Collections.reverse(list);
   
   
                   //next, convert the list back to String array
                   strDays = (String[]) list.toArray();
   
   
                   System.out.println(“String array reversed”);
   
   
                   //print the reversed String array
                   for(int i=0; i < strDays.length; i++){
                           System.out.println(strDays[i]);
                   }
   
   
           }
   
   
   }
   
   
   /*
   Output of above given Java Reverse String Array example would be
   String array reversed
   Wednesday
   Tuesday
   Monday
   Sunday
   */

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Input Stream to String Example

• /*
          Java InputStream to String Example
      This Java InputStream to String example shows how to convert InputStream to String in Java.
   */
  public class ConvertInputStreamToStringExample  
  {
  
  
          public static void main(String args[]) throws IOException{
  
  
                  //get InputStream of a file
                  InputStream is = new FileInputStream(“c:/data.txt”);
                  String strContent;
  
  
                  /*
                   * There are several way to convert InputStream to String. First is using
                   * BufferedReader as given below.
                   */
  
  
                  //Create BufferedReader object
                  BufferedReader bReader = new BufferedReader(new InputStreamReader(is));
                  StringBuffer sbfFileContents = new StringBuffer();
                  String line = null;
  
  
                  //read file line by line
                  while( (line = bReader.readLine()) != null) 
  {
                          sbfFileContents.append(line);
                  }
  
  
                  //finally convert StringBuffer object to String!
                  strContent = sbfFileContents.toString();
  
  
                  /*
                   * Second and one liner approach is to use Scanner class. This is only supported
                   * in Java 1.5 and higher version.
                   */
  
  
                  strContent = new Scanner(is).useDelimiter(“\\A”).next();
          }
  }

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Date to String Example

1. /*
           Java Date to String Example
           This Java Date to String example shows how to convert java.util.Date to
           String in Java.
    */
   
   
   import java.text.DateFormat;
   import java.text.SimpleDateFormat;
   import java.util.Date;
   
   
   public class ConvertDateToStringExample
    {
   
   
           public static void main(String args[]) 
   {
   
   
                   //create new java.util.Date object
                   Date date = new Date();
   
   
                   /*
                    * To convert java.util.Date to String, use SimpleDateFormat class.
                    */
   
   
                   /*
                    * crate new SimpleDateFormat instance with desired date format.
                    * We are going to use yyyy-mm-dd hh:mm:ss here.
                    */
                   DateFormat dateFormat = new SimpleDateFormat(“yyyy-mm-dd hh:mm:ss”);
   
   
                   //to convert Date to String, use format method of SimpleDateFormat class.
                   String strDate = dateFormat.format(date);
   
   
                   System.out.println(“Date converted to String: “ + strDate);
   
   
           }
   }
   
   
   /*
   Output of above given java.util.Date to String example would be
   Date converted to String: 2011-17-10 11:17:50
   */

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Char Array To String Example

• /*
          Java Char Array To String Example
          This Java char array to String example shows how to convert char array to
          String in Java.
   */
   
  public class CharArrayToStringExample 
  {
          public static void main(String args[]) 
  {
                  //char array
                  char[] charArray = new char[]{‘J’,‘a’,‘v’,‘a’};
                  /*
                   * To convert char array to String in Java, use
                   * String(Char[] ch) constructor of Java String class.
                   */
                 
                  String str = new String(charArray);
                  System.out.println(“Char array converted to String: “ + str);
          }
  }
  /*
  Output of above given char array to String example would be
  Char array converted to String: Java
  */

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ArrayList to String Array Example

1. /*
           Java ArrayList to String Array Example
           This Java ArrayList to String Array example shows how to convert ArrayList to String array
           in Java.
    */
   
   
   import java.util.ArrayList;
   import java.util.Arrays;
   
   
   public class ArrayListToStringArrayExample {
   
   
           public static void main(String args[]){
   
   
                   //ArrayList containing string objects
                   ArrayList<String> aListDays = new ArrayList<String>();
                   aListDays.add(“Sunday”);
                   aListDays.add(“Monday”);
                   aListDays.add(“Tuesday”);
   
   
                   /*
                    * To convert ArrayList containing String elements to String array, use
                    * Object[] toArray() method of ArrayList class.
                    *
                    * Please note that toArray method returns Object array, not String array.
                    */
                  
                   //First Step: convert ArrayList to an Object array.
                   Object[] objDays = aListDays.toArray();
   
   
                   //Second Step: convert Object array to String array
                   String[] strDays = Arrays.copyOf(objDays, objDays.length, String[].class);
   
   
                   System.out.println(“ArrayList converted to String array”);
   
   
                   //print elements of String array
                   for(int i=0; i < strDays.length; i++){
                           System.out.println(strDays[i]);
                   }
           }
   }
   
   
   /*
   Output of above given ArrayList to String Array example would be
   ArrayList converted to String array
   Sunday
   Monday
   Tuesday
   */

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Convert String to Character Array Example

1. /*
    Convert String to Character Array Example
    This example shows how to convert a given String object to an array
    of character
    */
   
   
   public class StringToCharacterArrayExample  
   {
   
   
     public static void main(String args[]) 
   {
       //declare the original String object
       String strOrig = “Hello World”;
       //declare the char array
       char[] stringArray;
   
   
       //convert string into array using toCharArray() method of string class
       stringArray = strOrig.toCharArray();
   
   
       //display the array
       for(int index=0; index < stringArray.length; index++)
         System.out.print(stringArray[index]);
   
   
     }
   
   
   }
   
   
   /*
   Output of the program would be :
   Hello World
   */

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Check if string contains valid number example

1. /*
           Check if string contains valid number example.
           This example shows how to check if string contains valid number
           or not using parseDouble and parseInteger methods of
           Double and Integer wrapper classes.
   */
   
   
   public class CheckValidNumberExample {
   
   
           public static void main(String[] args) {
   
   
                   String[] str = new String[]{“10.20”, “123456”, “12.invalid”};
   
   
                   for(int i=0 ; i < str.length ; i ++)
                   {
   
   
                           if( str[i].indexOf(“.”) > 0 )
                           {
   
   
                                   try
                                   {
                                           /*
                                            * To check if the number is valid decimal number, use
                                            * double parseDouble(String str) method of
                                            * Double wrapper class.
                                            *
                                            * This method throws NumberFormatException if the
                                            * argument string is not a valid decimal number.
                                            */
                                           Double.parseDouble(str[i]);
                                           System.out.println(str[i] + ” is a valid decimal number”);
                                   }
                                   catch(NumberFormatException nme)
                                   {
                                           System.out.println(str[i] + ” is not a valid decimal number”);
                                   }
   
   
                           }
                           else
                           {
                                   try
                                   {
                                           /*
                                            * To check if the number is valid integer number, use
                                            * int parseInt(String str) method of
                                            * Integer wrapper class.
                                            *
                                            * This method throws NumberFormatException if the
                                            * argument string is not a valid integer number.
                                            */
   
   
                                           Integer.parseInt(str[i]);
                                           System.out.println(str[i] + ” is valid integer number”);
                                   }
                                   catch(NumberFormatException nme)
                                   {
                                           System.out.println(str[i] + ” is not a valid integer number”);
                                   }
                           }
                   }
   
   
           }
   }
   
   
   
   /*
   Output would be
   10.20 is a valid decimal number
   123456 is valid integer number
   12.invalid is not a valid decimal number
   */

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A program to find whether no. is palindrome or not

Example : Input – 12521 is a palindrome no. Input – 12345 is not a palindrome no. */

class Palindrome
{
public static void main(String args[])
{
int num = Integer.parseInt(args[0]);
int n = num; //used at last time check
int reverse=0,remainder;
while(num > 0)
{
remainder = num % 10;
reverse = reverse * 10 + remainder;
num = num / 10;
}
if(reverse == n)
System.out.println(n+” is a Palindrome Number”);
else
System.out.println(n+” is not a Palindrome Number”);
}
}

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A program to Find whether number is Prime or Not

class PrimeNo
{
public static void main(String args[])
{
int num = Integer.parseInt(args[0]);
int flag=0;
for(int i=2;i<num;i++)
{
if(num%i==0)
{
System.out.println(num+” is not a Prime Number”);
flag = 1;
break;
}
}
if(flag==0)
System.out.println(num+” is a Prime Number”);
}
}

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Display Triangle as follow

1 2 3 4 5 6 7 8 9 10 … N */

class Output1{
public static void main(String args[])
{
int c=0;
int n = Integer.parseInt(args[0]);
loop1: for(int i=1;i<=n;i++)
{
loop2: for(int j=1;j<=i;j++)
{
if(c!=n)
{
c++;
System.out.print(c+” “);
}
else
break loop1;
}
System.out.print(“\n”);
}
}
}

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A program to find average of consecutive N Odd no. and Even no

class EvenOdd_Avg{
public static void main(String args[]){
int n = Integer.parseInt(args[0]);
int cntEven=0,cntOdd=0,sumEven=0,sumOdd=0;
while(n > 0){
if(n%2==0){
cntEven++;
sumEven = sumEven + n;
}
else{
cntOdd++;
sumOdd = sumOdd + n;
}
n–;
}
int evenAvg,oddAvg;
evenAvg = sumEven/cntEven;
oddAvg = sumOdd/cntOdd;
System.out.println(“Average of first N Even no is “+evenAvg);
System.out.println(“Average of first N Odd no is “+oddAvg);
}
}

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A program to generate Harmonic Series

Example : Input – 5 Output – 1 + 1/2 + 1/3 + 1/4 + 1/5 = 2.28 (Approximately) */
 
class HarmonicSeries
{
public static void main(String args[])
{
int num = Integer.parseInt(args[0]);
double result = 0.0;
while(num > 0)
{
result = result + (double) 1 / num;
num–;
}
System.out.println(“Output of Harmonic Series is “+result);
}
}

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Switch case demo

Example : Input – 124 Output – One Two Four */

class SwitchCaseDemo{
public static void main(String args[])
{
try
{
int num = Integer.parseInt(args[0]);
int n = num; //used at last time check
int reverse=0,remainder;
while(num > 0)
{
remainder = num % 10;
reverse = reverse * 10 + remainder;
num = num / 10;
}
String result=””; //contains the actual output
while(reverse > 0)
{
remainder = reverse % 10;
reverse = reverse / 10;
switch(remainder)
{
case 0 :
result = result + “Zero “;
break;
case 1 :
result = result + “One “;
break;
case 2 :
result = result + “Two “;
break;
case 3 :
result = result + “Three “;
break;
case 4 :
result = result + “Four “;
break;
case 5 :
result = result + “Five “;
break;
case 6 :
result = result + “Six “;
break;
case 7 :
result = result + “Seven “;
break;
case 8 :
result = result + “Eight “;
break;
case 9 :
result = result + “Nine “;
break;
default:
result=””;
}
}
System.out.println(result);
}catch(Exception e){
System.out.println(“Invalid Number Format”);
}
}
}

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A program to find whether given no. is Armstrong or not

Example : Input – 153 Output – 1^3 + 5^3 + 3^3 = 153, so it is Armstrong no. */

class Armstrong
{
public static void main(String args[])
{
int num = Integer.parseInt(args[0]);
int n = num; //use to check at last time
int check=0,remainder;
while(num > 0)
{
remainder = num % 10;
check = check + (int)Math.pow(remainder,3);
num = num / 10;
}
if(check == n)
System.out.println(n+” is an Armstrong Number”);
else
System.out.println(n+” is not a Armstrong Number”);
}
}

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A program to Display Invert Triangle using while loop

Example: Input – 5 Output : 5 5 5 5 5 4 4 4 4 3 3 3 2 2 1
class InvertTriangle
{
public static void main(String args[])
{
int num = Integer.parseInt(args[0]);
while(num > 0)
{
for(int j=1;j<=num;j++)
{
System.out.print(” “+num+” “);
}
System.out.print(“\n”);
num–;
}
}
}
 

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A program to convert given no. of days into months and days.(Assume that each month is of 30 days)

Example : Input – 69 Output – 69 days = 2 Month and 9 days */

class DayMonthDemo

{
public static void main(String args[])

{
int num = Integer.parseInt(args[0]);
int days = num%30;
int month = num/30;
System.out.println(num+” days = “+month+” Month and “+days+” days”);
}

}

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A program to Swap the values

class Swap{
public static void main(String args[]){
int num1 = Integer.parseInt(args[0]);
int num2 = Integer.parseInt(args[1]);
System.out.println(“\n***Before Swapping***”);
System.out.println(“Number 1 : “+num1);
System.out.println(“Number 2 : “+num2); //Swap logic
num1 = num1 + num2;
num2 = num1 – num2;
num1 = num1 – num2;
System.out.println(“\n***After Swapping***”);
System.out.println(“Number 1 : “+num1);
System.out.println(“Number 2 : “+num2);
}
}

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A program to find SUM AND PRODUCT of a given Digit

class Sum_Product_ofDigit{
public static void main(String args[]){
int num = Integer.parseInt(args[0]); //taking value as command line argument.
int temp = num,result=0; //Logic for sum of digit
while(temp>0){
result = result + temp;
temp–;
}
System.out.println(“Sum of Digit for “+num+” is : “+result); //Logic for product of digit
temp = num;
result = 1;
while(temp > 0){
result = result * temp;
temp–;
}
System.out.println(“Product of Digit for “+num+” is : “+result);
}
}

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A program to display a greet message according to Marks obtained by student

class SwitchDemo{
public static void main(String args[]){
int marks = Integer.parseInt(args[0]); //take marks
as command line argument.
switch(marks/10){
case 10:
case 9:
case 8:
System.out.println(“Excellent”);
break;
case 7:
System.out.println(“Very Good”);
break;
case 6:
System.out.println(“Good”);
break;
case 5:
System.out.println(“Work Hard”);
break;
case 4:
System.out.println(“Poor”);
break;
case 3:
case 2:
case 1:
case 0:
System.out.println(“Very Poor”);
break;
default:
System.out.println(“Invalid value Entered”);
}
}
}

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A Program that will read a float type value from the keyboard and print the following output

/*Small Integer not less than the number. Given Number. Largest Integer not greater than the number. */
class ValueFormat{
public static void main(String args[]){
double i = 34.32; //given number
System.out.println(“Small Integer not greater than the number :”+Math.ceil(i));
System.out.println(“Given Number : “+i);
System.out.println(“Largest Integer not greater than the number :”+Math.floor(i));
}

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To Find Minimum of Two Numbers using conditional operator

/* To find minimum of 2 Numbers using ternary operator */
class Minoftwo{
public static void main(String args[]){ //taking value as command line argument. //Converting String format to Integer value
int i = Integer.parseInt(args[0]);

int j = Integer.parseInt(args[1]);
int result = (i<j)?i:j;
System.out.println(result+” is a minimum value”);
}
}

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Find Maximum of Two Numbers

/* To Find Maximum of 2 Numbers using if else */
class Maxoftwo{
public static void main(String args[]){  
//taking value as command line argument. //Converting String format to Integer value
 
int i = Integer.parseInt(args[0]);
int j = Integer.parseInt(args[1]);
if(i > j)
System.out.println(i+” is greater than “+j);
else
System.out.println(j+” is greater than “+i);
}
}

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pyramid of numbers using for loops

/* Generate Pyramid For a Given Number Example This Java example shows how to generate a pyramid of numbers for given number using for loop example. */
import java.io.BufferedReader;
import java.io.InputStreamReader;
public class GeneratePyramidExample {
public static void main (String[] args) throws Exception{
BufferedReader keyboard = new BufferedReader (new
InputStreamReader(System.in));
System.out.println(“Enter Number:”);
int as= Integer.parseInt (keyboard.readLine());
System.out.println(“Enter X:”);
int x= Integer.parseInt (keyboard.readLine());
int y = 0;
for(int i=0; i<= as ;i++){
16
for(int j=1; j <= i ; j++){
System.out.print(y + “\t”);
y = y + x;
}
System.out.println(“”);
}
}
} /* Output of this example would be Enter Number: 5 Enter X: 1 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 ———————————————- Enter Number: 5 Enter X: 2 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 ———————————————- Enter Number: 5 Enter X: 3 0 3 6 9 12 15 18 21 24 27 30 33 36 39 42 */

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Factorial of a number using recursion

/*This program shows how to calculate Factorial of a number using recursion function. */
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
public class JavaFactorialUsingRecursion {
public static void main(String args[]) throws NumberFormatException,
IOException{
System.out.println(“Enter the number: “); //get input from the user
BufferedReader br=new BufferedReader(new
InputStreamReader(System.in));
int a = Integer.parseInt(br.readLine()); //call the recursive function to generate factorial
int result= fact(a);
System.out.println(“Factorial of the number is: ” + result);
}
static int fact(int b)
{
if(b <= 1) //if the number is 1 then return 1
return 1;
else //else call the same function with the value – 1
return b * fact(b-1);
}
} /* Output of this Java example would be Enter the number: 5 Factorial of the number is: 120 */

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Calculate Circle Area using radius

This program shows how to calculate
area of circle using it’s radius.
 
Example:-
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
public class CalculateCircleAreaExample {
public static void main(String[] args) {
int radius = 0;
System.out.println(“Please enter radius of a circle”);
try
{
//get the radius from console
BufferedReader br = new BufferedReader(new
InputStreamReader(System.in));
radius = Integer.parseInt(br.readLine());
}
//if invalid value was entered
catch(NumberFormatException ne)
{
System.out.println(“Invalid radius value” + ne);
System.exit(0);
}
catch(IOException ioe)
{
System.out.println(“IO Error :” + ioe);
System.exit(0);
}
/*
* Area of a circle is
* pi * r * r
* where r is a radius of a circle.
*/
//NOTE : use Math.PI constant to get value of pi
double area = Math.PI * radius * radius;
System.out.println(“Area of a circle is ” + area);
}
}

---

Output:-
Please enter radius of a circle
19
Area of a circle is 1134.1149479459152

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Nested Switch

This example shows how to use nested switch statements in a
java program.
Example:-
public class NestedSwitchExample {
public static void main(String[] args) {
/*
* Like any other Java statements, switch statements
* can also be nested in each other as given in
* below example.
*/
int i = 0;
int j = 1;
switch(i)
{
case 0:
switch(j)
{
case 0:
System.out.println(“i is 0, j is 0”);
break;
case 1:
System.out.println(“i is 0, j is 1”);
break;
default:
System.out.println(“nested default
case!!”);
}
break;
default:
System.out.println(“No matching case found!!”);
}
}
}

---

Output:-
i is 0, j is 1

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Reversed pyramid using for loops & decrements operator

Java Pyramid 5 Example
This Java Pyramid example shows how to generate pyramid or triangle
like given below using for loop.
12345
1234
123
12
1

Example:-
public class JavaPyramid5 {
public static void main(String[] args) {
for(int i=5; i>0 ;i–){
for(int j=0; j < i; j++){
System.out.print(j+1);
}
System.out.println(“”);
}
}
}

---

Output:-
12345
1234
123
12
1

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Pyramid of stars using nested for loops

/*
Java Pyramid 1 Example
This Java Pyramid example shows how to generate pyramid or triangle
like given below using for loop.
*
**
***
****
*****
*/

Example:-
public class JavaPyramid1 {
public static void main(String[] args) {
for(int i=1; i<= 5 ;i++){
for(int j=0; j < i; j++){
System.out.print(“*”);
}
//generate a new line
System.out.println(“”);
}
}
}

---

Output:-
*
**
***
****
*****

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Generate prime numbers between 1 & given number

Prime Numbers Java Example
This Prime Numbers Java example shows how to generate prime numbers
between 1 and given number using for loop.

Example:-
public class GeneratePrimeNumbersExample {
public static void main(String[] args) {
//define limit
int limit = 100;
System.out.println(“Prime numbers between 1 and ” + limit);
//loop through the numbers one by one
for(int i=1; i < 100; i++){
boolean isPrime = true;
//check to see if the number is prime
for(int j=2; j < i ; j++){
if(i % j == 0){
isPrime = false;
break;
}
}
// print the number
if(isPrime)
System.out.print(i + ” “);
}
}
}
Output:-
Prime numbers between 1 and 100
1 2 3 5 7 11 13 17 19 23 29 31 37 41 43 47 53 59 61 67 71 73 79 83 8

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