Java String charAt() 方法与示例

Java String charAt()方法返回指定索引处的字符。索引值应介于 0 和 length()-1 之间。
签名：

public char charAt(int index)  

范围：

index- Index of the character to be returned.

返回：

returns character at the specified position.

例外：

StringIndexOutOfBoundsException- If index is 
 negative or greater then the length of the 
 String.

示例：显示charAt()方法的工作原理

// Java program to demonstrate
// working of charAt() method
  
class Gfg {
    public static void main(String args[])
    {
        String s = "Welcome! to Geeksforgeeks Planet";
  
        char ch = s.charAt(3);
        System.out.println(ch);
  
        ch = s.charAt(0);
        System.out.println(ch);
    }
}

输出：

c
W

// Java program to demonstrate
// working of charAt() method
  
class Gfg {
    public static void main(String args[])
    {
        String s = "abc";
  
        char ch = s.charAt(4);
        System.out.println(ch);
    }
}

输出：

Exception in thread "main" java.lang.StringIndexOutOfBoundsException: String index out of range: 4
    at java.lang.String.charAt(String.java:658)
    at Gfg.main(File.java:9)

Java中的字符串类