Java Programming for Beginners

Learning to program means learning how to solve problems using code. This simple programming examples are fully intended for the beginners who have just started coding. It is a collection of progressively less difficult exercises that are suitable for people who just started learning . After completing this examples, you would be familiar with the basic Java programming skills and will also increase your logical thinking ability. In order to make good progress in your programming task, you need to test your work as early and as thoroughly as possible.

How to Find the Sum of Two Numbers in Java?

 
public class TestClass{
  public static void main(String[] args) {
    int x= 10;
    int y= 20;
    int sum =0;
    sum = x+y;
    System.out.println("Sum of numbers : "+sum);
  }
}

Find the average of the numbers in Java

 
public class TestClass{
  public static void main(String[] args) {
    int[] numbers = new int[]{10,20,30,40,50};
    int sum = 0;
    for(int i=0; i < numbers.length ; i++)
        sum = sum + numbers[i];
    double avg = sum / numbers.length;
    System.out.println("Average of numbers : "+avg);
  }
}

Check whether number is even or odd in Java?

The MODULUS Operator %

The modulus operator finds the modulus of its first operand with respect to the second. The % operator returns the remainder of two numbers. For instance 10 % 3 is 1 because 10 divided by 3 leaves a remainder of 1. You can use % just as you might use any other more common operator like + or -.

 
public class TestClass{
  public static void main(String[] args) {
    int x= 23;
    if(x%2 == 0){
      System.out.println("The number is Even");
    }
    else{
      System.out.println("The number is Odd");
    }
  }
}

Reverse a string in Java

 
public class TestClass{
  public static void main(String[] args) {
    String str = "TUTORIAL";
    char[] chr = str.toCharArray();
    int begin=0;
    int end=chr.length-1;
    char temp;
    while(end>begin){
        temp = chr[begin];
        chr[begin]=chr[end];
        chr[end] = temp;
        end--;
        begin++;
    }
    System.out.println(new String(chr));
  }
}

You can do this in another simple way by using StringBuilder Class in Java

 
public class TestClass{
  public static void main(String[] args) {
    String str = "TUTORIAL";
    String resStr = new StringBuilder(str).reverse().toString();
    System.out.println(resStr);
  }
}

Check whether string is palindrome or not in Java

 
public class TestClass{
  public static void main(String[] args) {
    String str = "ABCBA";
    boolean val = false;
    int n = str.length();
    for( int i = 0; i < n/2; i++ ){
      if (str.charAt(i) != str.charAt(n-i-1)){
      val = false;
        break;
      }else{
        val = true;
      }
    }
    if(val)
      System.out.println("String is Palindrome");
    else
      System.out.println("String is not Palindrome");
  }
}

You can do the same in another simple way

 
public class TestClass{
  public static void main(String[] args) {
    String str = "ABCBA";
    if(str.equals(new StringBuilder(str).reverse().toString()))
      System.out.println("String is Palindrome");
    else
      System.out.println("String is not Palindrome");
  }
}

Find the sum of all the numbers in an array in Java

 
public class TestClass{
  public static void main(String[] args) {
    int intArray[] = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10};
    int sum = 0;
    for (int x : intArray)
        sum += x;
    System.out.println("Sum of array elements : "+sum);
  }
}

Calculate Area of Triangle in Java

Area of a triangle can be calculated using the following formula, Area = (b*h)/2, where b is the base of the triangle and h is the vertical height of the triangle.

 
public class TestClass{
  public static void main(String[] args) {
    double tBase = 35.0;
    double tHeight = 210.5;
    double tArea = (tBase* tHeight)/2;
    System.out.println("Area of Triangle is: " + tArea);
  }
}

Fibonacci Series in Java

In fibonacci series, next number is the sum of previous two numbers for example 0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55 etc. Here set the limit as 10(int limit=10), you can change it as much as you want.

 
public class TestClass{
  public static void main(String[] args) {
		int limit = 10; //set the limit
		int x = -1;
		int y = 1;
		int z = 0;
		for(int i=1; i<=limit; i++) {
			z = x + y;
			int temp = x;
			x = y;
			y = z;
			System.out.println(z);
		}
  }
}

Find duplicate characters in a String in Java

The following example find duplicate characters in a String and count the number of occurances using Java

 
public class TestClass{
  public static void main(String[] args) {
    String input = "java tutorial";
    int cnt=0;
    int strLen=0;
    do{
      try{
        char chrInput[]=input.toCharArray();
        strLen=chrInput.length;
        cnt=0;
        for(int j=0;j<strLen;j++){
          if((chrInput[0]==chrInput[j])&&((chrInput[0]>=65&&chrInput[0]<=91)(chrInput[0]>=97&&chrInput[0]<=123)))
          cnt++;
        }
        if(cnt!=0)
          System.out.println(chrInput[0]+" "+cnt+" Times");
        input=input.replace(""+chrInput[0],"");
      }catch(Exception ex){
        ex.printStackTrace();
      }
    }while(strLen!=1);
  }
}

Convert binary to decimal number in Java

 
public class TestClass{
public static void main(String[] args) {
  String str = "100";
  double j=0;
  for(int i=0;i<str.length();i++){
    if(str.charAt(i)== '1'){
      j=j+ Math.pow(2,str.length()-1-i);
    }
  }
    System.out.println("Decimal Number is :" + j);
  }
}

Decimal to Binary Conversion in Java

 
public class TestClass{
  public static void main(String[] args) {
    int input = 55, i = 0, temp[] = new int[10];
    int bArray[];
    while (input > 0) {
      temp[i++] = input % 2;
      input /= 2;
    }
     bArray = new int[i];
    int k = 0;
    for (int j = i - 1; j >= 0; j--) {
      bArray[k++] = temp[j];
      System.out.print(temp[j]);
    }
  }
}

Largest and Smallest Number from an Array in Java

 
public class TestClass{
  public static void main(String[] args) {
  int input[] = new int[]{200,10,100,90,20,80,150};
  int smallNum = input[0];
  int largeNum = input[0];
  for(int i=1; i< input.length; i++){
    if(input[i] > largeNum)
      largeNum = input[i];
    else if (input[i] < smallNum)
      smallNum = input[i];
  }
  System.out.println("Largest Number is : " + largeNum);
  System.out.println("Smallest Number is : " + smallNum);
  }
}

Next : Java if-else statement