Java BufferedInputStream mark()用法及代码示例

Java中BufferedInputStream类的mark()方法用于标记输入流中的当前位置。在mark()方法之后，调用相同类BufferedInputStream的Reset()方法。 Reset()将位置固定在最后标记的位置，以便可以再次读取相同的字节。

常规合同：输入流以某种方式保存了在调用mark()方法之后读取的所有字节，并在调用reset()方法时再次返回相同的字节。仅当markSupported()返回true时，才执行此操作。但是，如果在调用reset()方法之前读取的字节超过了readlimit字节，则输入流不需要保存任何数据。

用法:

public void mark(int readlimit)

覆盖：重写FilterInputStream类的mark()方法。

参数：此方法接受一个Integer类型的参数readlimit，它表示标记位置变为无效之前可以读取的最大字节数限制。

返回值：此方法不返回任何值。

异常：此方法不会引发任何异常。

以下示例程序旨在说明IO包中BufferedInputStream类中的mark()方法：
程序1:假设存在文件“c:/demo.txt”。

// Java program to illustrate 
// BufferedInputStream mark() method 
  
import java.io.*; 
  
public class GFG { 
    public static void main(String[] args) 
    { 
  
        // Create input stream 'demo.txt' 
        // for reading containing text "GEEKS" 
        FileInputStream inputStream 
            = new FileInputStream( 
                "c:/demo.txt"); 
  
        // Convert inputStream to 
        // bufferedInputStream 
        BufferedInputStream buffInputStr 
            = new BufferedInputStream( 
                inputStream); 
  
        // Read and print characters one by one 
        System.out.println( 
            "Char:"
            + (char)buffInputStr.read()); 
        System.out.println( 
            "Char:"
            + (char)buffInputStr.read()); 
        System.out.println( 
            "Char:"
            + (char)buffInputStr.read()); 
  
        // Mark is set on the input stream 
        buffInputStr.mark(0); 
  
        System.out.println( 
            "Char:"
            + (char)buffInputStr.read()); 
  
        // Reset() is invoked 
        buffInputStr.reset(); 
  
        // Read and print characters 
        System.out.println( 
            "Char:"
            + (char)buffInputStr.read()); 
        System.out.println( 
            "Char:"
            + (char)buffInputStr.read()); 
    } 
}

输出：

Char:G
Char:E
Char:E
Char:K
Char:K
Char:S

程序2:假设存在文件“c:/demo.txt”。

// Java program to illustrate 
// BufferedInputStream.mark() method 
import java.io.*; 
public class GFG { 
    public static void main(String[] args) 
    { 
  
        // Create input stream 'demo.txt' 
        // for reading containing text 
        // "GEEKSFORGEEKS" 
        FileInputStream inputStream 
            = new FileInputStream( 
                "c:/demo.txt"); 
  
        // Convert inputStream to 
        // bufferedInputStream 
        BufferedInputStream buffInputStr 
            = new BufferedInputStream( 
                inputStream); 
  
        // Read and print characters one by one 
        System.out.println( 
            "Char:"
            + (char)buffInputStr.read()); 
        System.out.println( 
            "Char:"
            + (char)buffInputStr.read()); 
        System.out.println( 
            "Char:"
            + (char)buffInputStr.read()); 
        System.out.println( 
            "Char:"
            + (char)buffInputStr.read()); 
  
        // Mark is set on the input stream 
        buffInputStr.mark(0); 
  
        System.out.println( 
            "Char:"
            + (char)buffInputStr.read()); 
  
        // Reset() is invoked 
        buffInputStr.reset(); 
  
        // read and print characters 
        System.out.println( 
            "Char:"
            + (char)buffInputStr.read()); 
        System.out.println( 
            "Char:"
            + (char)buffInputStr.read()); 
        System.out.println( 
            "Char:"
            + (char)buffInputStr.read()); 
        System.out.println( 
            "Char:"
            + (char)buffInputStr.read()); 
    } 
}

输出：

Char:G
Char:E
Char:E
Char:K
Char:S
Char:S
Char:F
Char:O
Char:R

参考文献：
https://docs.oracle.com/javase/10/docs/api/java/io/BufferedInputStream.html#mark(int)

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注：本文由纯净天空筛选整理自pp_pankaj大神的英文原创作品 BufferedInputStream mark() 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。