Hello guys, I have been sharing a lot of Programming interview questions and coding problems to learn programming better which is appreciated by you guys. In this post, I have come with other simple programming problems for Java beginners. I love to share short programming problems because they help in developing programming sense. Many people will argue against simple problems like prime numbers, palindrome, and factorial, but I really find them useful, especially for beginners. A beginner is far away to solve a complex data structure problem or even more complex problems like those that appear in TopCoder or other programming sites. Programmers learn gradually and they need the joy of doing something and seeing results much quicker than any other. Small success motivates them. Anyway, here is our problem statement, you need to write a Java program to find the top two maximum numbers in the given array. You can not use any sorting functions and you should iterate the array only once. The use of any kind of collection class like TreeSet or LinkedHashSet is also not allowed. For example, if the given integer array is [20, 34, 21, 87, 92, 2147483647] then the first maximum is 2147483647 and the second maximum is 92. Bonus points are for those, who can also write JUnit test cases, more test scenarios, more points. Few more bonus points for those who can write code to deal with a really large array, something which may not entirely fit on memory. Btw, a good knowledge of fundamental data structure like an array is very important for every programmer. If you need to brush up your algorithms skills or want to learn data structure in depth then and need a course then I highly recommend Data Structure and Algorithms in Java: Deep Dive on Udemy. It's both comprehensive and enjoyable and also very affordable. You can buy it for just $10 on Udemy sale. How to Find Top Two Maximum Numbers from Integer Array Here is our sample Java program, It solves the problem following the given problem statement and under constraints states. For example, it doesn't use any sorting algorithm like bubble sort or quicksort, or Collections.sort() method. As I said before, this kind of program is a good exercise for mastering basic building blocks of any programming language like loops, if-else block, and learning relational operators like less than (<) and greater than (>). It takes advantage of the if-else control statement to solve this problem. All we do is start with two variables as max1 and max2 and initialized them with Integer.MIN_VALUE, which is the limit of minimum value. Now we iterate through the array and compare each number against these two numbers, if the current number is greater than max1 then max1 = number, and max2 = max1. Otherwise if it only greater than max2 then we only update max2 with the current number. At the end of the iteration, max1 and max2 point to the top two numbers from a given array. You see the problem solved without any utility class or third-party library. Though, if you are new to Java and not very familiar with the conditional statements in Java like the if-else-if block or switch statement then also recommend you check out a comprehensive Java course like The Complete Java MasterClass to learn Java better. This is also very affordable and you can buy in just $9.99 on crazy Udemy sales. Java Program To Find Top Two Numbers from Integer Array Now, without wasting any more of your time, here is our complete code example which you can copy-paste in Eclipse or your favorite IDE and run it. You can also save this code in a file called TopTwoMaximum.java and run it from the command prompt. import java.util.Arrays; /** * Java program to find top two maximum numbers from an integer array. * * @author http://java67.blogspot.com */ public class TopTwoMaximum{ public static void main(String args[]) { topTwo(new int[]{20, 34, 21, 87, 92, Integer.MAX_VALUE}); topTwo(new int[]{0, Integer.MIN_VALUE, -2}); topTwo(new int[]{Integer.MAX_VALUE, 0, Integer.MAX_VALUE}); topTwo(new int[]{1, 1, 0}); } public static void topTwo(int[] numbers) { int max1 = Integer.MIN_VALUE; int max2 = Integer.MIN_VALUE; for (int number : numbers) { if (number > max1) { max2 = max1; max1 = number; } else if (number > max2) { max2 = number; } } System.out.println("Given integer array : " + Arrays.toString(numbers)); System.out.println("First maximum number is : " + max1); System.out.println("Second maximum number is : " + max2); } } Output: Given integer array : [20, 34, 21, 87, 92, 2147483647] First maximum number is : 2147483647 Second maximum number is : 92 Given integer array : [0, -2147483648, -2] First maximum number is : 0 Second maximum number is : -2 Given integer array : [2147483647, 0, 2147483647] First maximum number is : 2147483647 Second maximum number is : 2147483647 Given integer array : [1, 1, 0] First maximum number is : 1 Second maximum number is : 1 From the output, you can see that our method the topTwo(int[] numbers) is working properly for different sets of inputs. I have chosen the main method over the JUnit test for testing my code, which is quick and dirty. JUnit testing provides you more options and a better framework to write test cases. If you don't know how to write a JUnit test case, see that link. It explains that in detail. That's all on how to find two maximum from integer array in Java. How about extending it further and finding the top three numbers from the integer array? Can you do that without any help? Once you have done that, You can probably try finding the top three minimum numbers from the array. For example, if the given array is [11, 2, 5, 4] then the top three minimum numbers are 2, 4, and 5. You can even extend this logic even to find the largest and smallest number in an array, as shown in that example Other Programming Interview Questions and Articles for Java developers How to reverse an array in place in Java? 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(solution) Top 50 Java Programs from Coding Interviews (see here) 5 Free Data Structure and Algorithms Courses for Programmers (courses) 10 Algorithms Books Every Programmer Should Read (books) How to find duplicates from an unsorted array in Java? (solution) How to remove duplicates from an array in Java? (solution) Thanks for reading this article so far. If you like this coding tutorial then please share it with your friends and colleagues. If you have any questions or doubt then please let us know and I'll try to find an answer for you. As always suggestions, comments, innovative and better answers are most welcome. P. S. - If you are looking for some Free Algorithms courses to improve your understanding of Data Structure and Algorithms, then you should also check the Data Structure in Java free course on Udemy. It's completely free and all you need to do is create a free Udemy account to enroll in this course.