pushBack()
方法pushBack()方法在java.io包中可用。
pushBack()方法用于使该StreamTokenizer的下一次调用返回ttype字段中的当前值,而不更新nval或sval字段值。
pushBack()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。
pushBack()方法在推回时不会引发异常。
语法:
Public void pushBack();
参数:
它不接受任何参数。
返回值:
该方法的返回类型为void,不返回任何内容。
示例
// Java程序演示示例 // pushBack()StreamTokenizer的void方法 import java.io.*; public class PushBack { public static void main(String[] args) { String str = "Hi, This is \n a mathematical expression :\n " + " 2 * 4 = 8 " + "8 + 5 = 13"; try { //实例化FileOutputStream和ObjectOutputStream- FileOutputStream fos_stm = new FileOutputStream("D:\\includehelp.txt"); ObjectOutputStream obj_out_stm = new ObjectOutputStream(fos_stm); //通过使用writeUTF()方法是 //将给定的字符串写入文件 obj_out_stm.writeUTF(str); obj_out_stm.flush(); //实例化FileOutputStream和ObjectOutputStream- ObjectInputStream obj_in_stm = new ObjectInputStream(new FileInputStream("D:\\includehelp.txt")); //实例化StreamTokenizer和Reader- Reader reader = new BufferedReader(new InputStreamReader(obj_in_stm)); StreamTokenizer st = new StreamTokenizer(reader); //在这里,我们开始考虑 //文件不为空 boolean end_of_file = false; do { //通过使用nextToken()方法是 //解析流中的下一个标记 int token = st.nextToken(); switch (token) { case StreamTokenizer.TT_EOF: System.out.println("End of File Found"); end_of_file = true; break; case StreamTokenizer.TT_EOL: System.out.println("End of Line Found"); 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 + " Found."); } //通过使用pushBack()方法是 //返回最后一个令牌 st.pushBack(); token = st.nextToken(); switch (token) { case StreamTokenizer.TT_EOF: System.out.println("End of File Found"); end_of_file = true; break; case StreamTokenizer.TT_EOL: System.out.println("End of Line Found"); 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 + " Found."); } } while (!end_of_file); } catch (Exception ex) { ex.printStackTrace(); } } }
输出结果
@ Found. @ Found. word: Hi word: Hi , Found. , Found. word: This word: This word: is word: is word: a word: a word: mathematical word: mathematical word: expression word: expression : Found. : Found. number: 2.0 number: 2.0 * Found. * Found. number: 4.0 number: 4.0 = Found. = Found. number: 8.0 number: 8.0 number: 8.0 number: 8.0 + Found. + Found. number: 5.0 number: 5.0 = Found. = Found. number: 13.0 number: 13.0 End of File Found End of File Found