Java uses the indexOf() function of the StringBuilder class to find the specified substring in the string

Java uses the indexOf() function of the StringBuilder class to find the specified substring in the string

In Java programming, it is often necessary to perform various operations on strings, including finding specified substrings. In order to improve the search efficiency, we can use Java's StringBuilder class and the indexOf() function it provides to implement the function of finding substrings.

First we need to understand what the StringBuilder class is. The StringBuilder class is a variable string class in Java that can dynamically increase and decrease the length of a string and change the content of the string. Compared with the String class, the StringBuilder class is more efficient and is especially suitable for scenarios where string content is frequently modified.

When using the indexOf() function of StringBuilder, you need to first create a StringBuilder object and add the parent string you need to find through the append() function. Then, use the indexOf() function to find the first occurrence of the specified substring in the parent string.

The following is a sample code that shows how to use StringBuilder's indexOf() function to find a specified substring in a string:

public class SearchSubstring {
    public static void main(String[] args) {
        StringBuilder sb = new StringBuilder("Hello, world!");

        // 查找指定子串的位置
        int index = sb.indexOf("world");

        if (index != -1) {
            System.out.println("子串在父串中的位置为：" + index);
        } else {
            System.out.println("未找到指定子串！");
        }
    }
}

In the above code, we first create a StringBuilder object sb, and use the append() function to add the string "Hello, world!" to sb. Then, use the indexOf() function to find the first occurrence of the substring "world" in sb.

If the search is successful, the index value returned is the index position of the substring in the parent string; if the search fails, -1 is returned. In this example, since the substring "world" exists in the parent string, the output result is "The position of the substring in the parent string is: 7".

It should be noted that the indexOf() function searches for the position of the substring from front to back. If you want to find the last occurring position, you can use the lastIndexOf() function. In addition, when using the indexOf() function, you can also specify a starting position to limit the search range.

To sum up, by using the indexOf() function of Java's StringBuilder class, we can easily find the specified substring in the string. This method is efficient and flexible, very suitable for processing string search scenarios, and brings great convenience to our programming work. I hope the sample code in this article can help readers better understand and use the indexOf() function.

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