How to Efficiently Check Character Occurrence in a String in Java?

Checking Character Occurrence in a String Efficiently

In Java, determining whether a single character appears in a string can be performed without the overhead of loops. One efficient approach is to utilize the indexOf() method.

The indexOf() method, when passed a character as an argument, scans the input string for the first occurrence of that character. If the character is found, its index is returned. However, if the character is not present in the string, the method returns -1.

For example, consider the following code:

<code class="java">String str = "Hello World";
char toFind = 'a';
int index = str.indexOf(toFind);</code>

If the character 'a' appears in the string, the index variable will be assigned its index (e.g., 1). Otherwise, the index variable will contain -1.

This approach is significantly more efficient than iterating through the entire string using a loop. It avoids the repeated comparisons and allows for a constant-time operation in most practical scenarios.

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