java.io.StreamTokenizer.pushBack() 方法會導致此標記生成器的nextToken方法的下一次調用返回的當前值在ttype字段和不修改的值在nval或sval 字段中。

聲明

以下是java.io.StreamTokenizer.pushBack()方法的聲明

public void pushBack()

參數

• NA

返回值

這個方法冇有返回值

異常

• NA

例子

下麵的示例演示java.io.StreamTokenizer.pushBack()方法的用法。

package com.yiibai;

import java.io.*;

public class StreamTokenizerDemo {

   public static void main(String[] args) {

      String text = "Hello. This is a text 
 that will be split "
              + "into tokens. 1+1=2";
      try {
         // create a new file with an ObjectOutputStream
         FileOutputStream out = new FileOutputStream("test.txt");
         ObjectOutputStream oout = new ObjectOutputStream(out);

         // write something in the file
         oout.writeUTF(text);
         oout.flush();

         // create an ObjectInputStream for the file we created before
         ObjectInputStream ois =
                 new ObjectInputStream(new FileInputStream("test.txt"));

         // create a new tokenizer
         Reader r = new BufferedReader(new InputStreamReader(ois));
         StreamTokenizer st = new StreamTokenizer(r);

         // specify that numbers should be parsed
         st.parseNumbers();

         // print the stream tokens
         boolean eof = false;
         do {

            int token = st.nextToken();

            switch (token) {
               case StreamTokenizer.TT_EOF:
                  System.out.println("End of File encountered.");
                  eof = true;
                  break;
               case StreamTokenizer.TT_EOL:
                  System.out.println("End of Line encountered.");
                  break;
               case StreamTokenizer.TT_WORD:
                  System.out.println("Word: " + st.sval);
                  break;
               case StreamTokenizer.TT_NUMBER:
                  System.out.println("Number: " + st.nval);
                  break;
               default:
                  System.out.println((char) token + " encountered.");
                  if (token == '!') {
                     eof = true;
                  }
            }

            // pushback the last token
            st.pushBack();

            token = st.nextToken();

            switch (token) {
               case StreamTokenizer.TT_EOF:
                  System.out.println("End of File encountered.");
                  eof = true;
                  break;
               case StreamTokenizer.TT_EOL:
                  System.out.println("End of Line encountered.");
                  break;
               case StreamTokenizer.TT_WORD:
                  System.out.println("Word: " + st.sval);
                  break;
               case StreamTokenizer.TT_NUMBER:
                  System.out.println("Number: " + st.nval);
                  break;
               default:
                  System.out.println((char) token + " encountered.");
                  if (token == '!') {
                     eof = true;
                  }
            }
         } while (!eof);


      } catch (Exception ex) {
         ex.printStackTrace();
      }
   }
}

讓我們來編譯和運行上麵的程序，這將產生以下結果：

Word: Hello.
Word: Hello.
Word: This
Word: This
Word: is
Word: is
Word: a
Word: a
Word: text
Word: text
Word: that
Word: that
Word: will
Word: will
Word: be
Word: be
Word: split
Word: split
Word: into
Word: into
Word: tokens.
Word: tokens.
Number: 1.0
Number: 1.0
+ encountered.
+ encountered.
Number: 1.0
Number: 1.0
= encountered.
= encountered.
Number: 2.0
Number: 2.0
End of File encountered.
End of File encountered