PushbackReader類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()方法用于標(biāo)記此流中的當(dāng)前位置，并且此方法在調(diào)用期間引發(fā)異常。

• 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()方法是一種非靜態(tài)方法，只能通過類對(duì)象訪問，如果嘗試使用類名稱訪問該方法，則會(huì)收到錯(cuò)誤消息。

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

  mark()方法在標(biāo)記流時(shí)可能會(huì)引發(fā)異常。

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

  IOException：當(dāng)此流不支持mark()方法時(shí)，可能引發(fā)此異常。

Syntax:

句法：

public void mark(int r_limit);

Parameter(s):

參數(shù)：

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

  int r_limit –表示標(biāo)記無(wú)效之前可以讀取的字符數(shù)限制。

Return value:

返回值：

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

該方法的返回類型為void ，不返回任何內(nèi)容。

Example:

例：

// Java program to demonstrate the example // of void mark(int r_limit) method of // PushbackReaderimport 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 PushbackReaderr_stm = new StringReader("Java World!!!!");pb_r = new PushbackReader(r_stm);// By using read() method isto // read the character from pb_rchar 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_rSystem.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() methodSystem.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 streamif (r_stm != null) {r_stm.close();if (pb_r != null) {pb_r.close();}}}} }

Output

輸出量

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

翻譯自: https://www.includehelp.com/java/pushbackreader-mark-method-with-example.aspx

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