Java String indexOf（String substr）方法与示例

2024-04-19 06:59:04 361

字符串indexOf（Stringsubstr）方法

indexOf（Stringsubstr）是Java中的String方法，用于获取字符串中指定子字符串的索引。

如果字符串中存在子字符串，则返回第一次出现的索引，如果字符串中不存在子字符串，则返回-1。

语法：

int str_object.indexOf(String substr);

这里，

str_object是主字符串的对象，我们必须在其中找到给定子字符串的索引。

substr是字符串中要在字符串中找到的部分。

它接受子字符串并返回其首次出现的索引；如果字符串中不存在子字符串，则返回-1。

示例

    Input: 
    String str = "NHOOO"

    Function call:
    str.indexOf("Help")

    Output:
    7

    Input: 
    String str = "NHOOO"

    Function call:
    str.indexOf("HELP)

    Output:
    -1

Java代码演示String.indexOf()方法的示例

public class Main
{
    public static void main(String[] args) {
        String str = "NHOOO";
        String substr = "";
        int index;
        
        substr = "Help";
        index = str.indexOf(substr);
        if(index != -1)
            System.out.println(substr + " is found at " + index + " position.");
        else 
            System.out.println(substr + " does not found.");

        substr = "lude";
        index = str.indexOf(substr);
        if(index != -1)
            System.out.println(substr + " is found at " + index + " position.");
        else 
            System.out.println(substr + " does not found.");            

        substr = "HELP";
        index = str.indexOf(substr);
        if(index != -1)
            System.out.println(substr + " is found at " + index + " position.");
        else 
            System.out.println(substr + " does not found.");
    }
}

输出结果

Help is found at 7 position.
lude is found at 3 position.
HELP does not found.

Java String indexOf（String substr）方法与示例

字符串indexOf（Stringsubstr）方法

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