字符串indexOf(int ch，int fromIndex)方法 (String indexOf(int ch, int fromIndex) Method)

indexOf(int ch, int fromIndex) is a String method in Java and it is used to get the index of a specified character in the string from given fromIndex. That means to search for the character will start from the given index (fromIndex).

indexOf(int ch，int fromIndex)是Java中的String方法，用于從給定的fromIndex獲取字符串中指定字符的索引。 這意味著搜索字符將從給定索引( fromIndex )開始。

If the character exists in the string from fromIndex, it returns the index of the first occurrence of the character, if the character does not exist in the string, it returns -1.

如果該字符存在于fromIndex的字符串中，則返回該字符首次出現的索引，如果該字符不存在于字符串中，則返回-1。

Syntax:

句法：

int str_object.indexOf(int ch, int fromIndex);

Here,

這里，

• str_object is an object of main string in which we have to find the index of given character.

  str_object是主字符串的對象，我們必須在其中找到給定字符的索引。

• chr is a character to be found in the string.

  chr是在字符串中找到的字符。

• fromIndex is the position in main string from where we method will start the searching for the character.

  fromIndex是主字符串在其中我們方法將開始搜索字符的位置。

It accepts a character, from index and returns an index of its first occurrence or -1 if the character does not exist in the string.

它從index接受一個字符，并返回其首次出現的索引；如果字符串中不存在該字符，則返回-1。

Example:

例：

Input: String str = "IncludeHelp"Function call:str.indexOf('H', 4)Output:7Input: String str = "IncludeHelp"Function call:str.indexOf('W', 2)Output:-1

Java code to demonstrate the example of String.indexOf() method

Java代碼演示String.indexOf()方法的示例

public class Main {public static void main(String[] args) {String str = "IncludeHelp";char ch;int index;ch = 'H';index = str.indexOf(ch, 4);if(index != -1)System.out.println(ch + " is found at " + index + " position.");else System.out.println(ch + " does not found.");ch = 'e';index = str.indexOf(ch, 3);if(index != -1)System.out.println(ch + " is found at " + index + " position.");else System.out.println(ch + " does not found."); ch = 'W';index = str.indexOf(ch, 2);if(index != -1)System.out.println(ch + " is found at " + index + " position.");else System.out.println(ch + " does not found."); } }

Output

輸出量

H is found at 7 position. e is found at 6 position. W does not found.

翻譯自: https://www.includehelp.com/java/string-indexOf-int-ch-fromindex-method-with-example.aspx

總結

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