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
