Use java's StringBuilder.indexOf() function to find the position of a substring in the string buffer

Use Java's StringBuilder.indexOf() function to find the position of a substring in the string buffer

String operations are one of the commonly used operations in programming, and in Java, we often use The class is StringBuilder. StringBuilder is a mutable string sequence in Java. It provides rich methods to edit, connect and operate strings.

In string operations, sometimes we need to find the position of a certain substring in the string buffer. StringBuilder's indexOf() function is designed for this purpose. It can help us quickly find the location of the substring, so as to facilitate subsequent operations.

Now, let us understand how to use the StringBuilder.indexOf() function through code examples.

public class StringBuilderExample {
    public static void main(String[] args) {
        // 创建一个StringBuilder对象
        StringBuilder sb = new StringBuilder("Hello, world!");

        // 查找子字符串的位置
        int index = sb.indexOf("world");

        // 输出结果
        if (index != -1) {
            System.out.println("子字符串的位置为：" + index);
        } else {
            System.out.println("未找到子字符串");
        }
    }
}

In the above example, we first created a StringBuilder object and assigned the string "Hello, world!" to it. We then use the indexOf() function to find the location of the substring "world" in the string buffer. If the substring is found, the index position is returned; otherwise, -1 is returned. Finally, we perform corresponding output based on the returned results.

Run the above code, the output result is: "The position of the substring is: 7". This means that the position of the substring "world" in the string "Hello, world!" starts at index 7. Note that in this example, we only found the first occurrence of the "world" substring.

At the same time, we can also use the overloaded version of the indexOf() function to find the position of the substring. For example, we can specify the index position to start the search, and the substring to find. The following is a modified code example:

public class StringBuilderExample {
    public static void main(String[] args) {
        // 创建一个StringBuilder对象
        StringBuilder sb = new StringBuilder("Hello, world!");

        // 查找子字符串的位置，从索引5开始查找
        int index = sb.indexOf("world", 5);

        // 输出结果
        if (index != -1) {
            System.out.println("子字符串的位置为：" + index);
        } else {
            System.out.println("未找到子字符串");
        }
    }
}

In the modified code, we specify the starting position of the search by passing in two parameters in the indexOf() function. In this way, we can limit the scope of the search. In the above example, we search for the substring "world" starting from index 5. Since "world" starts at index 7, the output result is: "The position of the substring is: 7".

In short, in Java, you can use the StringBuilder.indexOf() function to quickly find the position of a substring in the string buffer. By using this function rationally, we can edit and operate strings more flexibly, improving the efficiency and readability of the code. I hope the code examples in this article will be helpful to you.

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