Java Programs


Nearest Smallest Prime



  • Program to find the nearest smaller prime number for a given integer; use a function to decide whether a number is prime or not.

Program

import java.util.Scanner;

public class NearPrime {

            private static Scanner sc;
            static int num;
            public int prime(int j) {
                        int flag=0;
                        for(int i=1;i<=j;i++) {
                                    if(j%i==0) {
                                                flag++;
                                    }
                        }
            if(flag==2) {
                        System.out.println("The nearest smaller prime number for "+num+" is "+j);
                        return 1;
            }
            else {
                        return 0;
            }
           
}
            public static void main(String[] args) {
           
                        int i,check=0;
                        sc=new Scanner(System.in);
                        System.out.print("Enter a number:");
                        num=sc.nextInt();
                        NearPrime ob = new NearPrime();
                        for(i=num-1;i>=0;i--) {
                                    check=ob.prime(i);
                                    if(check==1) {
                                                return;
                                    }
                        }
                        if(check==0) {
                                    System.out.println("There is no nearest smaller prime number for "+num+".");
                        }
            }

}

Output

Enter a number:89
The nearest smaller prime number for 89 is 83

Decimal to Binary Conversion

Program to convert a number in decimal system to binary system. Hint: use recursion.

Program

import java.util.Scanner;

public class DecimalToBinary {

            private static Scanner assign;
            public static void main(String[] args) {
                        int dec;
                        assign=new Scanner(System.in);
                        System.out.println("Enter a decimal value:");
                        dec=assign.nextInt();
                        System.out.println("The binary value of "+dec+" is:");
                        DecimalToBinary ob=new DecimalToBinary();
                        ob.compute(dec);
            }
            public void compute(int dec) {
                        if(dec>0) {
                                    compute(dec/2);
                                    System.out.print(dec%2+" ");
                        }
            }

}

Output

Enter a decimal value:
98
The binary value of 98 is:

1 1 0 0 0 1 0

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