Java Array Exercises: Find a missing number in an array

Java Array: Exercise-24 with Solution

Write a Java program to find a missing number in an array.

Pictorial Presentation:

Java Array Exercises: Find a missing number in an array

Sample Solution:

Java Code:

import java.util.*;
public class Exercise24 {
 public static void main(String[] args) {

   int total_num;
   int[] numbers = new int[]{1,2,3,4,6,7};
   total_num = 7;
   int expected_num_sum = total_num * ((total_num + 1) / 2);
   int num_sum = 0;
   for (int i: numbers) {
    num_sum += i;
       System.out.print( expected_num_sum - num_sum);

Sample Data: 1,2,3,4,6,7

Sample Output:



Flowchart: Java exercises: Find a missing number in an array

Visualize Java code execution (Python Tutor):

Java Code Editor:

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Java: Tips of the Day

Different between parseInt() and valueOf() in java?

Well, the API for Integer.valueOf(String) does indeed say that the String is interpreted exactly as if it were given to Integer.parseInt(String). However, valueOf(String) returns a new Integer() object whereas parseInt(String) returns a primitive int.

If you want to enjoy the potential caching benefits of Integer.valueOf(int), you could also use this eyesore:

Integer k = Integer.valueOf(Integer.parseInt("123"))

Now, if what you want is the object and not the primitive, then using valueOf(String) may be more attractive than making a new object out of parseInt(String) because the former is consistently present across Integer, Long, Double, etc.

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