Java Reader read()用法及代码示例

Java中Reader类的read()方法用于从流中读取单个字符。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。

该方法被声明为抽象方法。这意味着，如果在读取字符时需要更改所需的操作，则Reader抽象类的子类应重写此方法。

用法:

public abstract int read()

参数：此方法不接受任何参数

返回值：此方法返回一个整数值，该整数值是从流中读取的整数值。范围从0到65535。如果未读取任何字符，则返回-1。

异常：如果输入输出时发生某些错误，则此方法将引发IOException。

下面的方法说明了read()方法的用法方式：

示例1:

// Java program to demonstrate 
// Reader read() method 
  
import java.io.*; 
import java.util.*; 
  
class GFG { 
    public static void main(String[] args) 
    { 
  
        try { 
  
            String str = "GeeksForGeeks"; 
  
            // Create a Reader instance 
            Reader reader 
                = new StringReader(str); 
  
            // Get the character 
            // to be read from the stream 
            int ch; 
  
            // Read the first 5 characters 
            // to this reader using read() method 
            // This will put the str in the stream 
            // till it is read by the reader 
            for (int i = 0; i < 5; i++) { 
                ch = reader.read(); 
                System.out.println("\nInteger value "
                                   + "of character read: "
                                   + ch); 
                System.out.println("Actual "
                                   + "character read: "
                                   + (char)ch); 
            } 
  
            reader.close(); 
        } 
        catch (Exception e) { 
            System.out.println(e); 
        } 
    } 
}

输出：

Integer value of character read: 71
Actual character read: G

Integer value of character read: 101
Actual character read: e

Integer value of character read: 101
Actual character read: e

Integer value of character read: 107
Actual character read: k

Integer value of character read: 115
Actual character read: s

示例2:

// Java program to demonstrate 
// Reader read() method 
  
import java.io.*; 
import java.util.*; 
  
class GFG { 
    public static void main(String[] args) 
    { 
  
        try { 
            String str = "GeeksForGeeks"; 
  
            // Create a Reader instance 
            Reader reader 
                = new StringReader(str); 
  
            // Get the character 
            // to be read from the stream 
            int ch; 
  
            // Read the first character 
            // to this reader using read() method 
            // This will put the str in the stream 
            // till it is read by the reader 
            ch = reader.read(); 
            System.out.println("\nInteger value "
                               + "of character read: "
                               + ch); 
            System.out.println("Actual "
                               + "character read: "
                               + (char)ch); 
  
            reader.close(); 
        } 
        catch (Exception e) { 
            System.out.println(e); 
        } 
    } 
}

输出：

Integer value of character read: 71
Actual character read: G

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

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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() 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。