Java PushbackReader read(char, int, int)用法及代码示例

Java中的PushbackReader类的read(char []，int，int)方法用于将指定长度的字符以指定的偏移量读取到数组中。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(char[] charArray, 
                     int offset, 
                     int length)

参数：此方法接受三个强制参数：

charArray这是要写入流中的字符数组。
offset这是要在数组中写入字符的偏移量索引。
length这是要写入数组的字符数。

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。
IndexOutOfBoundsException：如果偏移值不在字符数组范围内

以下方法说明了read(char []，int，int)方法的用法方式：

程序1:

// Java program to demonstrate 
// PushbackReader read(char, int, int) method 
  
import java.io.*; 
import java.util.*; 
  
class GFG { 
    public static void main(String[] args) 
    { 
  
        try { 
            // Initializing a StringReader 
            // and PushbackReader 
            String s = "GeeksForGeeks"; 
  
            StringReader stringReader 
                = new StringReader(s); 
            PushbackReader pushbackReader 
                = new PushbackReader(stringReader); 
  
            // Get the character array 
            // to be read from the stream 
            char[] charArray = new char[5]; 
  
            // Get the offset index 
            int offset = 0; 
  
            // Get the length 
            int length = 5; 
  
            // Read the charArray 
            // to this reader using read() method 
            // This will put the str in the stream 
            // till it is read by the reader 
            pushbackReader 
                .read(charArray, offset, length); 
  
            // Print the read charArray 
            System.out.println( 
                Arrays.toString(charArray)); 
  
            // Close the stream 
            pushbackReader.close(); 
            System.out.println("Stream Closed."); 
        } 
        catch (Exception e) { 
            System.out.println(e); 
        } 
    } 
}

输出：

[G, e, e, k, s]
Stream Closed.

程序2:

// Java program to demonstrate 
// PushbackReader read(char, int, int) method 
  
import java.io.*; 
import java.util.*; 
  
class GFG { 
    public static void main(String[] args) 
    { 
  
        try { 
            // Initializing a StringReader 
            // and PushbackReader 
            String s = "GFG"; 
  
            StringReader stringReader 
                = new StringReader(s); 
            PushbackReader pushbackReader 
                = new PushbackReader(stringReader); 
  
            // Get the character array 
            // to be read from the stream 
            char[] charArray = new char[5]; 
  
            // Get the offset index 
            int offset = 0; 
  
            // Get the length 
            int length = 2; 
  
            // Read the charArray 
            // to this reader using read() method 
            // This will put the str in the stream 
            // till it is read by the reader 
            pushbackReader 
                .read(charArray, offset, length); 
  
            // Print the read charArray 
            System.out.println( 
                Arrays.toString(charArray)); 
  
            // Close the stream 
            pushbackReader.close(); 
            System.out.println("Stream Closed."); 
        } 
        catch (Exception e) { 
            System.out.println(e); 
        } 
    } 
}

输出：

[G, F,,, ]
Stream Closed.

参考： https://docs.oracle.com/javase/9/docs/api/java/io/PushbackReader.html#read-char:A-int-int-

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注：本文由纯净天空筛选整理自srinam大神的英文原创作品 PushbackReader read(char, int, int) 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。