Check out example codes for "Java program to display prime numbers from 1 to 100". It will help you in understanding the concepts better.

Code Example 1

public class PrimeNumbersFrom1To100
{
   public static void main(String[] args)
   {
      int maxNumber = 100;
      boolean prime = true;
      String primeNumbers = "";
      for(int a = 1; a <= maxNumber; a++)
      {
         prime = checkPrime(a);
         if(prime)
         {
            primeNumbers = primeNumbers + a + " ";
         }
      }
      System.out.println("Display prime numbers from 1 to " + maxNumber + ": ");
      System.out.println(primeNumbers);
   }
   public static boolean checkPrime(int number)
   {
      int remainder;
      for(int a = 2; a <= number / 2; a++)
      {
         remainder = number % a;
         // if remainder is equal to 0 then number is not prime
         if(remainder == 0)
         {
            return false;
         }
      }
      return true;
   }
}

Code Example 2

Now let’s learn java program to print prime numbers in a given range.

public class PrimeNumberRangeDemo 
{
   public static void main(String[] args) 
   {
      int lowerRange = 10, higherRange = 50;  
      while(lowerRange < higherRange) 
      {
         boolean flag = false;
         for(int a = 2; a <= lowerRange / 2; ++a) 
         {
            if(lowerRange % a == 0)
            {
               flag = true;
               break;
            }
         }
         if(!flag && lowerRange != 0 && lowerRange != 1)
             System.out.print(lowerRange + " ");
         ++lowerRange;
      }
   }
}

Code Example 3

class PrimeNumbers
{
   public static void main (String[] args)
   {		
       int i =0;
       int num =0;
       //Empty String
       String  primeNumbers = "";

       for (i = 1; i <= 100; i++)         
       { 		  	  
          int counter=0; 	  
          for(num =i; num>=1; num--)
	  {
             if(i%num==0)
	     {
 		counter = counter + 1;
	     }
	  }
	  if (counter ==2)
	  {
	     //Appended the Prime number to the String
	     primeNumbers = primeNumbers + i + " ";
	  }	
       }	
       System.out.println("Prime numbers from 1 to 100 are :");
       System.out.println(primeNumbers);
   }
}

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