Java Reader read(CharBuffer)用法及代码示例

Java中Reader类的read(CharBuffer)方法用于将指定的字符读取到CharBuffer实例中。此方法将流阻塞到：

它已从流中获取了一些输入。
发生了一些IOException
阅读时已到达流的末尾。

用法:

public int read(CharBuffer charBuffer)

参数：此方法接受强制参数charBuffer，该参数是要在Stream中写入的CharBuffer实例。

返回值：此方法返回一个整数值，该整数值是从流中读取的字符数。如果未读取任何字符，则返回-1。

异常：此方法引发以下异常：

IOException：输入输出时发生错误。
NullPointerException ：如果要填充的CharBuffer实例为null
ReadOnlyBufferException：如果要填充的CharBuffer实例是只读缓冲区

下面的方法说明了read(CharBuffer)方法的用法方式：

示例1:

// Java program to demonstrate 
// Reader read(CharBuffer) method 
  
import java.io.*; 
import java.util.*; 
import java.nio.CharBuffer; 
  
class GFG { 
    public static void main(String[] args) 
    { 
  
        try { 
  
            String str = "GeeksForGeeks"; 
  
            // Create a Reader instance 
            Reader reader 
                = new StringReader(str); 
  
            // Get the CharBuffer instance 
            // to be read from the stream 
            CharBuffer charBuffer 
                = CharBuffer.allocate(5); 
  
            // Read the charBuffer 
            // to this reader using read() method 
            // This will put the str in the stream 
            // till it is read by the reader 
            reader.read(charBuffer); 
  
            // Print the read charBuffer 
            System.out.println(charBuffer 
                                   .flip() 
                                   .toString()); 
  
            reader.close(); 
        } 
        catch (Exception e) { 
            System.out.println(e); 
        } 
    } 
}

输出：

Geeks

示例2:

// Java program to demonstrate 
// Reader read(CharBuffer) method 
  
import java.io.*; 
import java.util.*; 
import java.nio.CharBuffer; 
  
class GFG { 
    public static void main(String[] args) 
    { 
  
        try { 
  
            String str = "GeeksForGeeks"; 
  
            // Create a Reader instance 
            Reader reader 
                = new StringReader(str); 
  
            // Get the CharBuffer instance 
            // to be read from the stream 
            CharBuffer charBuffer 
                = CharBuffer 
                      .allocate( 
                          str.length()); 
  
            // Read the charBuffer 
            // to this reader using read() method 
            // This will put the str in the stream 
            // till it is read by the reader 
            reader.read(charBuffer); 
  
            // Print the read charBuffer 
            System.out.println(charBuffer 
                                   .flip() 
                                   .toString()); 
  
            reader.close(); 
        } 
        catch (Exception e) { 
            System.out.println(e); 
        } 
    } 
}

输出：

GeeksForGeeks

参考： https://docs.oracle.com/javase/9/docs/api/java/io/Reader.html#read-java.nio.CharBuffer-

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注：本文由纯净天空筛选整理自Code_r大神的英文原创作品 Reader read(CharBuffer) method in Java with Examples。非经特殊声明，原始代码版权归原作者所有，本译文未经允许或授权，请勿转载或复制。