字符串indexOf(String substr，int fromIndex)方法 (String indexOf(String substr, int fromIndex) Method)
indexOf(String substr, int fromIndex) is a String method in Java and it is used to get the index of a specified substring in the string from given fromIndex. That means to search for the substring will start from the given index (fromIndex).
indexOf(String substr，int fromIndex)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。 这意味着从指定索引( fromIndex )开始搜索子字符串。
If substring exists in the string from fromIndex, it returns the index of the first occurrence of the substring, if substring does not exist in the string, it returns -1.
如果从的fromIndex字符串中存在串，它返回字符串的第一个出现的位置，如果子字符串没有字符串中存在，则返回-1。
Syntax:
句法：
int str_object.indexOf(String substr, int fromIndex);
Here,
这里，
str_object is an object of main string in which we have to find the index of given substring.
str_object是主字符串的对象，在其中我们必须找到给定子字符串的索引。
substr is the part of the string to be found in the string.
substr是要在字符串中找到的字符串的一部分。
fromIndex is an index of the main string, from where method will start searching for the substring.
fromIndex是主字符串的索引，方法将从该索引开始搜索子字符串。
It accepts a substring, from index and returns index of its first occurrence or -1 if substring does not exist in the string.
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。
Example:
例：
Input:
String str = "IncludeHelp"
Function call:
str.indexOf("Help", 4)
Output:
7
Input:
String str = "IncludeHelp"
Function call:
str.indexOf("HELP, 2)
Output:
-1
Java code to demonstrate the example of String.indexOf() method
Java代码演示String.indexOf()方法的示例
public class Main
{
public static void main(String[] args) {
String str = "IncludeHelp";
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.");
}
}
Output
输出量
Help is found at 7 position.
lude does not found.
HELP does not found.
翻译自: https://www.includehelp.com/java/string-indexOf-String-substr-int-fromindex-method-with-example.aspx
)
)
)
