Java PushbackReader mark（）方法与示例

PushbackReader类mark()方法 (PushbackReader Class mark() method)

• mark() method is available in java.io package.

  mark()方法在java.io包中可用。

• mark() method is used to mark the current position in this stream and this method throws an exception during the call.

  mark()方法用于标记此流中的当前位置，并且此方法在调用期间引发异常。

• mark() method is a non-static method, it is accessible with the class object only and if we try to access the method with the class name then we will get an error.

  mark()方法是一种非静态方法，只能通过类对象访问，如果尝试使用类名称访问该方法，则会收到错误消息。

• mark() method may throw an exception at the time of marking the stream.

  mark()方法在标记流时可能会引发异常。

  IOException: This exception may throw when this stream unsupport mark() method.

  IOException：当此流不支持mark()方法时，可能引发此异常。

Syntax:

句法：

    public void mark(int r_limit);

Parameter(s):

参数：

• int r_limit – represents limit on the number of characters that can be read before the mark gets invalid.

  int r_limit –表示标记无效之前可以读取的字符数限制。

Return value:

返回值：

The return type of the method is void, it returns nothing.

该方法的返回类型为void ，不返回任何内容。

Example:

例：

// Java program to demonstrate the example 
// of void mark(int r_limit) method of
// PushbackReader

import java.io.*;

public class MarkOfPBR {
    public static void main(String[] args) throws Exception {
        Reader r_stm = null;
        PushbackReader pb_r = null;
        try {
            // Instantiates Reader and PushbackReader
            r_stm = new StringReader("Java World!!!!");
            pb_r = new PushbackReader(r_stm);

            // By using read() method isto 
            // read the character from pb_r
            char ch1 = (char) pb_r.read();
            char ch2 = (char) pb_r.read();
            char ch3 = (char) pb_r.read();

            System.out.println("ch1: " + ch1);
            System.out.println("ch2: " + ch2);
            System.out.println("ch3: " + ch3);

            // By using mark() method isto
            // set the current position in this
            // pb_r
            System.out.println("pb_r.mark(1): ");
            pb_r.mark(1);
            char ch4 = (char) pb_r.read();
            char ch5 = (char) pb_r.read();

            System.out.println("ch4: " + ch4);
            System.out.println("ch5: " + ch5);

            // By using reset() method isto
            // reset the stream to the position 
            // set by the call mark() method

            System.out.println("pb_r.reset(): ");
            pb_r.reset();
            char ch6 = (char) pb_r.read();
            char ch7 = (char) pb_r.read();
            char ch8 = (char) pb_r.read();

            System.out.println("ch4: " + ch6);
            System.out.println("ch5: " + ch7);
            System.out.println("ch6: " + ch8);
        } catch (Exception ex) {
            System.out.println("Mark Not Supported");
        } finally {
            // with the help of this block is to
            // free all necessary resources linked
            // with the stream
            if (r_stm != null) {
                r_stm.close();
                if (pb_r != null) {
                    pb_r.close();
                }
            }
        }
    }
}

Output

输出量

ch1: J
ch2: a
ch3: v
pb_r.mark(1): 
Mark Not Supported

翻译自: https://www.includehelp.com/java/pushbackreader-mark-method-with-example.aspx