indexOf(int ch,int fromIndex)是Java中的String方法,用于从给定的fromIndex获取字符串中指定字符的索引。这意味着搜索字符将从给定索引(fromIndex)开始。
如果fromFromIndex的字符串中存在该字符,则返回该字符首次出现的索引,如果字符串中不存在该字符,则返回-1。
语法:
int str_object.indexOf(int ch, 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字符的索引。
chr是要在字符串中找到的字符。
fromIndex是主字符串在其中我们方法将开始搜索字符的位置。
它从index接受一个字符,并返回其首次出现的索引;如果字符串中不存在该字符,则返回-1。
示例
Input: String str = "NHOOO" Function call: str.indexOf('H', 4) Output: 7 Input: String str = "NHOOO" Function call: str.indexOf('W', 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"; 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."); } }
输出结果
H is found at 7 position. e is found at 6 position. W does not found.