Efficient Char Comparison in Java

General Discussions
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1

What is the shortest way to check if a char variable is one of 21 specific characters in Java? I tried using if(symbol == ('A'|'B'|'C')){} but it doesn’t seem to work. Do I need to write it explicitly like if(symbol == 'A' || symbol == 'B' ...)? How to compare chars in Java efficiently in this case?

2

When you’re just getting started, the simplest way to check if a char is one of a few specific characters is to use an OR (||) condition. It’s easy to understand and does the job, like so:

if (symbol == 'A' || symbol == 'B' || symbol == 'C') {
    // Do something
}

This works fine for a handful of characters. However, if you have many characters (like 21 in your case), it starts to look a bit unwieldy. Let’s dive into a cleaner option for how to compare chars in Java.

3

Exactly! If you have more than a couple of characters to check, using a String can make things a bit more manageable. You can store all your valid characters in a String and use the indexOf() method to check if your symbol is in it. Here’s how:

if ("ABCXYZ123!@#".indexOf(symbol) != -1) {
    // Do something
}

This approach is much shorter, easier to read, and you don’t have to manually write out a bunch of || conditions. indexOf() checks if the character exists in the string and returns the position (or -1 if it’s not found). This is a good option for a moderate number of characters, but let’s see how we can go even further, especially if you’re frequently checking for these symbols.

4

Right, when you’re dealing with a larger number of characters, or need to check this frequently, a Set is a great way to optimize the lookup. A Set in Java offers faster lookups since it allows constant-time complexity for the contains() method. Here’s how to set it up:

import java.util.Set;

Set<Character> validSymbols = Set.of('A', 'B', 'C', 'X', 'Y', 'Z', '1', '2', '3', '!', '@', '#');
if (validSymbols.contains(symbol)) {
    // Do something
}

This way, you get faster performance, and your code is nice and clean. It’s especially helpful when you need to check for many characters often. This is probably the most efficient way to handle how to compare chars in Java when your list grows.