5 Tricky Java Programming Problems

1. Find the maximum and minimum value of a triplet without using conditional statements

Given three integers, find the maximum and minimum number between them without using any conditional statement (if, switch) or ternary operator.

Solution 1. Using short-circuiting in Boolean expressions

Briefly, short-circuiting is when in some boolean expression like a && b && ... && d (where a..z — some expressions) we skip execution of the rest of the expression if the previous part guarantees us some boolean value. For example, expression true || b guarantees us true because of the first value, so we’re not going to execute b expression.

So let’s put this approach into our solution:

Solution 2. Using repeated subtraction

Note: this solution works with positive integers

2. Swap two numbers without using a third variable in one line (Java)

Given two integers, swap them in a single line in Java.

Let’s suppose we have two variables: x and y.

Solution 1. Using Bitwise XOR (^) Operator

We have ^ operation. And in Java assignment may be an expression that returns an assigned value. Let’s use both facts together:

Solution 2. Using Addition and Subtraction Operator

Solution 3. Using Multiplication and Division Operator

3. Multiply two numbers without using a multiplication operator or loops

Given two integers, multiply them without using the multiplication operator or loops.

Solution

As we know, multiplication is summing x value y times. This would be easy if we could use loops. But we also may use recursion instead:

4. Print “Hello World” with an empty main

Solution 1. Using static block

When our program tries to run main, it runs static block before:

Solution 2. Initialize field using a static method

Solution 3. Initialize inner static class

Solution 4. Call static variable from outer class

Solution

We may rewrite the expression n*15 as n*15 = n*16 - n = (n << 4) - n