Java中的 CharBuffer charAt() 方法及示例

Java.nio.CharBuffer类的charAt()方法用于读取相对于当前位置的给定索引处的字符。

句法：

public final char charAt(int index)

参数：此方法采用要读取的字符的索引，相对于位置；必须是非负数且小于剩余（）。

返回值：此方法返回索引位置（）+索引处的字符。

异常：如果索引的先决条件不成立，此方法将抛出IndexOutOfBoundsException 。

下面是说明 charAt(int index) 方法的示例：

示例 1：

// Java program to demonstrate
// charAt() method
  
import java.nio.*;
import java.util.*;
  
public class GFG {
    public static void main(String[] args)
    {
        // Creating the CharBuffer
        try {
  
            // creating object of CharBuffer
            // and allocating size capacity
            CharBuffer charbuffer
                = CharBuffer.allocate(3);
  
            // append the value in CharBuffer
            // using append() method
            charbuffer.append('a')
                .append('b')
                .append('c')
                .rewind();
  
            // print the CharBuffer
            System.out.println("Original CharBuffer:  "
                               + Arrays.toString(
                                     charbuffer.array()));
  
            // Read char at particular Index
            // using charAt() method
            char value = charbuffer.charAt(2);
  
            // Display the value
            System.out.println("\nvalue at Index 0 is : "
                               + value);
        }
  
        catch (IndexOutOfBoundsException e) {
  
            System.out.println("\nindex is greater than"
                               + " the capacity minus 1");
            System.out.println("Exception throws : " + e);
        }
    }
}

输出：

Original CharBuffer:  [a, b, c]

value at Index 0 is : c

示例 2：演示 IndexOutOfBoundsException。

// Java program to demonstrate
// charAt() method
  
import java.nio.*;
import java.util.*;
  
public class GFG {
    public static void main(String[] args)
    {
        // Creating the CharBuffer
        try {
  
            // creating object of CharBuffer
            // and allocating size capacity
            CharBuffer charbuffer
                = CharBuffer.allocate(3);
  
            // append the value in CharBuffer
            // using append() method
            charbuffer.append('a')
                .append('b')
                .append('c')
                .rewind();
  
            // print the CharBuffer
            System.out.println("Original CharBuffer:  "
                               + Arrays.toString(
                                     charbuffer.array()));
  
            // Read char at particular Index
            // using charAt() method
            char value = charbuffer.charAt(3);
  
            // Display the value
            System.out.println("\nvalue at Index 0 is : "
                               + value);
        }
  
        catch (IndexOutOfBoundsException e) {
  
            System.out.println("\nindex is greater than"
                               + " the capacity minus 1");
            System.out.println("Exception throws : " + e);
        }
    }
}

输出：

Original CharBuffer:  [a, b, c]

index is greater than the capacity minus 1
Exception throws : java.lang.IndexOutOfBoundsException

参考： https://docs.oracle.com/javase/9/docs/api/ Java/nio/CharBuffer.html#charAt-int-