问题描述：在字符串中寻找特定字符
1、第1次出现位置
实现函数原型： int indexOf(char c)
Java代码：
import java.io.*;
public class Way_1
{public static void main(String args[]){String str = "Geeks for Geeks is a computer science portal";System.out.println(str.length());int firstIndex = str.indexOf('s');System.out.println("First occurrence of char 's' is found at: " + firstIndex);int firstIn = str.indexOf('z');System.out.println("First occurrence of char 'z' is found at: " + firstIn); }
}
样例字符串： Geeks for Geeks is a computer science portal
样例输出：
2、最后一次出现位置
实现函数原型： public int lastIndexOf(char c)
Java代码：
import java.io.*;
public class Way_2
{public static void main(String args[]){String str = "Geeks for Geeks is a computer science portal";System.out.println(str.length());int lastIndex = str.lastIndexOf('s');System.out.println("Last occurrence of char 's' is found at: " + lastIndex); int lastIn = str.lastIndexOf('z');System.out.println("Last occurrence of char 'z' is found at: " + lastIn); }
}
样例字符串： Geeks for Geeks is a computer science portal
样例输出：
3、指定位置后的首次出现
实现函数原型： public int IndexOf(char c, int indexFrom)
说明： 除-1外，该函数的返回值必然大于或等于其第2个参数indexFrom。
Java代码：
import java.io.*;public class String_Search
{public static void main(String [] args){String str = "Geeks For Geeks is a computer science portal";System.out.println(str.length());int first_in = str.indexOf('s', 10);System.out.println("First occurrence of char 's' after index 10: " + first_in);int first_not_in = str.indexOf('z', 10);System.out.println("First occurrence of char 'z' after index 10: " + first_not_in);}
}
样例字符串： Geeks For Geeks is a computer science portal
样例输出：
4、指定位置前的末次出现
实现函数原型： public int lastIndexOf(char c, int fromIndex)
说明： 除-1外，该函数的返回值必然小于或等于其第2个参数fromIndex。
Java代码：
import java.io.*;public class String_Search_2
{public static void main(String [] args){String str = "Geeks For Geeks is a computer science portal";System.out.println(str.length());int lastIndex = str.lastIndexOf('s', 20);System.out.println("Last occurrence of char 's' before index 20: " + lastIndex);int last_not_in = str.lastIndexOf('z', 20);System.out.println("Last occurrence of char 'z' before index 20: " + last_not_in);}
}
样例字符串： Geeks For Geeks is a computer science portal
样例输出：
5、指定位置的字符
实现函数原型： char charAt(int indexNumber)
说明： 若指定的下标indexNumber超出字符串长度范围，则抛出StringIndexOutOfBounds异常。
Java代码：
import java.io.*;public class Character_At
{public static void main(String [] args){String str = "Geeks For Geeks is a computer science portal";System.out.println(str.length());int char_at = str.charAt(20);System.out.println("Character at location 20: " + char_at);int char_not_at = str.charAt(60);}
}
样例字符串： Geeks For Geeks is a computer science portal
样例输出：
