Java中的 Reader reset() 方法和示例

Java中Reader类的reset()方法用于重置流。重置后，如果流已被标记，则此方法尝试将其重新定位在标记处，否则将尝试将其定位到起始位置。

句法：

public void reset()

参数：此方法不接受任何参数。

返回值：此方法不返回任何值。

异常：此方法抛出 IOException：

• 如果输入输出时出现错误
• 如果流没有被标记
• 如果商标已失效
• 如果不支持 reset() 方法。

下面的方法说明了 reset() 方法的工作：

方案一：

// Java program to demonstrate
// Reader reset() 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 10 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 < 10; i++) {
                ch = reader.read();
                System.out.print((char)ch);
            }
  
            System.out.println();
  
            // mark the stream for
            // 5 characters using reset()
            reader.mark(5);
  
            // reset the stream position
            reader.reset();
  
            // Read the 5 characters from marked position
            // to this reader using read() method
            for (int i = 0; i < 5; i++) {
                ch = reader.read();
                System.out.print((char)ch);
            }
        }
        catch (Exception e) {
            System.out.println(e);
        }
    }
}

输出：

GeeksForGe
eks??

方案二：

// Java program to demonstrate
// Reader reset() 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 10 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 < 10; i++) {
                ch = reader.read();
                System.out.print((char)ch);
            }
  
            System.out.println();
  
            // reset the stream position
            reader.reset();
  
            // Read the 5 characters from marked position
            // to this reader using read() method
            for (int i = 0; i < 5; i++) {
                ch = reader.read();
                System.out.print((char)ch);
            }
        }
        catch (Exception e) {
            System.out.println(e);
        }
    }
}

输出：

GeeksForGe
Geeks

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