Java StreamTokenizer lineno()用法及代碼示例

StreamTokenizer類lineno()方法

• lineno() 方法可在java.io包。
• lineno() 方法用於返回此 StreamTokenizer 的當前行號。
• lineno() 方法是一個非靜態方法，它隻能通過類對象訪問，如果我們嘗試使用類名訪問方法，那麽我們將得到一個錯誤。
• lineno() 方法返回行號時不拋出異常。

用法:

    public int lineno();

參數：

• 它不接受任何參數。

返回值：

該方法的返回類型是int，它獲取此 StreamTokenizer 的當前行號。

例：

// Java program to demonstrate the example 
// of int lineno() method of StreamTokenizer

import java.io.*;

public class LineNo {
    public static void main(String[] args) {
        String str = "Hi, This is a mathematical expression:\n" +
            " 2 * 4 = 8" + "8 + 5 = 13";

        try {
            // Instantiates FileOutputStream  and ObjectOutputStream 
            FileOutputStream fos_stm = new FileOutputStream("D:\\includehelp.txt");
            ObjectOutputStream obj_out_stm = new ObjectOutputStream(fos_stm);

            // By using writeUTF() method is to
            // write the given string in the file
            obj_out_stm.writeUTF(str);
            obj_out_stm.flush();

            // Instantiates FileOutputStream  and ObjectOutputStream 
            ObjectInputStream obj_in_stm = new ObjectInputStream(new FileInputStream("D:\\includehelp.txt"));

            // Instantiates StreamTokenizer and Reader
            Reader reader = new BufferedReader(new InputStreamReader(obj_in_stm));
            StreamTokenizer st = new StreamTokenizer(reader);

            // By using eolIsSignificant() method is to
            // set the end of line treats as whitespace
            // i.e "\n"considers as whitespace instead of
            // End of Line found
            st.eolIsSignificant(false);


            // By using lineno() method is to 
            // return the present line number
            // in this st
            int line_num = st.lineno();
            System.out.println("st.lineno():" + line_num);

            // Here, we are considering initially 
            // file is not empty
            boolean end_of_file = false;

            while (!end_of_file) {
                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.");
                }
            }
        } catch (Exception ex) {
            ex.printStackTrace();
        }
    }
}

輸出

st.lineno():1
= Found.
word:Hi
, Found.
word:This
word:is
word:a
word:mathematical
word:expression
:Found.
number:2.0
* Found.
number:4.0
= Found.
number:88.0
+ Found.
number:5.0
= Found.
number:13.0
End of File Found