w3resource

Java Exercises: Multiply two specified integers without using the multiply operator

Java Basic: Exercise-168 with Solution

Write a Java program to multiply two given integers without using the multiply operator(*).

Sample Solution:

Java Code:

import java.util.*;
public class Solution {	
  public static int multiply(int n1, int n2) {
    int result = 0;
    boolean negative_num = (n1 < 0 && n2 >= 0) || (n2 < 0 && n1 >= 0);
    boolean positive_num = !negative_num;
    n1 = Math.abs(n1);
    for (int i = 0; i < n1; i++) {
      if (negative_num && n2 > 0 || positive_num && n2 < 0)
        result -= n2;
      else
        result += n2;
    }

    return result;
 }

   public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        System.out.print("Input the first number: ");
        int n1 = in.nextInt();
		System.out.print("Input the second number: ");
        int n2 = in.nextInt();
		System.out.println("\nResult: " + multiply(n1,n2));		
		}

}

Sample Output: 

Input the first number:  25
Input the second number:  5

Result: 125

Flowchart:

Flowchart: Java exercises: Multiply two specified integers without using the multiply operator.

Java Code Editor:

Contribute your code and comments through Disqus.

Previous: Write a Java program to move every zero to the right side of a given array of integers.
Next: Write a Java program to reverse the content of a sentence (assume a single space between two words) without reverse every word.

What is the difficulty level of this exercise?



Java: Tips of the Day

Array vs ArrayLists:

The main difference between these two is that an Array is of fixed size so once you have created an Array you cannot change it but the ArrayList is not of fixed size. You can create instances of ArrayLists without specifying its size. So if you create such instances of an ArrayList without specifying its size Java will create an instance of an ArrayList of default size.

Once an ArrayList is full it re-sizes itself. In fact, an ArrayList is internally supported by an array. So when an ArrayList is resized it will slow down its performance a bit as the contents of the old Array must be copied to a new Array.

At the same time, it's compulsory to specify the size of an Array directly or indirectly while creating it. And also Arrays can store both primitives and objects while ArrayLists only can store objects.

Ref: https://bit.ly/3o8L2KH