Java.io.StreamTokenizer.pushBack() 方法
描述
java.io.StreamTokenizer.pushBack() 方法导致对该标记器的 nextToken 方法的下一次调用返回 ttype 字段中的当前值，而不是修改 nval 或 sval 中的值 场地。
声明
以下是 java.io.StreamTokenizer.pushBack() 方法的声明。
public void pushBack()
参数
NA
返回值
此方法不返回值。
异常
NA
示例
下面的例子展示了 java.io.StreamTokenizer.pushBack() 方法的使用。
package com.tutorialspoint;
import java.io.*;
public class StreamTokenizerDemo {
public static void main(String[] args) {
String text = "Hello. This is a text \n 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();
}
}
}
让我们编译并运行上面的程序，这将产生下面的结果 −
Word: AHello. Word: AHello. 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.
