Java String indexOf（String substr，int fromIndex）方法，带示例

2024-04-19 06:58:05 332

字符串indexOf（Stringsubstr，intfromIndex）方法

indexOf（Stringsubstr，intfromIndex）是Java中的String方法，用于从给定的fromIndex获取字符串中指定子字符串的索引。这意味着搜索子字符串将从给定索引(fromIndex)开始。

如果fromfrom的字符串中存在子字符串，则返回该子字符串首次出现的索引，如果该字符串中不存在子字符串，则返回-1。

语法：

int str_object.indexOf(String substr, int fromIndex);

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。

fromIndex是主字符串的索引，方法将从该索引开始搜索子字符串。

它从索引接受子字符串，并返回其第一次出现的索引；如果字符串中不存在子字符串，则返回-1。

示例

    Input: 
    String str = "NHOOO"

    Function call:
    str.indexOf("Help", 4)

    Output:
    7

    Input: 
    String str = "NHOOO"

    Function call:
    str.indexOf("HELP, 2)

    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, 4);
        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, 8);
        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, 2);
        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 does not found.
HELP does not found.

Java String indexOf（String substr，int fromIndex）方法，带示例

字符串indexOf（Stringsubstr，intfromIndex）方法

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