java 如何在java中标记输入文件
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How to tokenize an input file in java
提问by syakirah ibrahim
i'm doing tokenizing a text file in java. I want to read an input file, tokenize it and write a certain character that has been tokenized into an output file. This is what i've done so far:
我正在用 java 标记一个文本文件。我想读取一个输入文件，对其进行标记并将已标记的某个字符写入输出文件。这是我到目前为止所做的：
package org.apache.lucene.analysis;
import java.io.BufferedReader;
import java.io.File;
import java.io.FileReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.StreamTokenizer;
class StringProcessing {
// Create BufferedReader class instance
public static void main(String[] args) throws IOException {
InputStreamReader input = new InputStreamReader(System.in);
BufferedReader keyboardInput = new BufferedReader(input);
System.out.print("Please enter a java file name: ");
String filename = keyboardInput.readLine();
if (!filename.endsWith(".DAT")) {
System.out.println("This is not a DAT file.");
System.exit(0);
}
File File = new File(filename);
if (File.exists()) {
FileReader file = new FileReader(filename);
StreamTokenizer streamTokenizer = new StreamTokenizer(file);
int i = 0;
int numberOfTokensGenerated = 0;
while (i != StreamTokenizer.TT_EOF) {
i = streamTokenizer.nextToken();
numberOfTokensGenerated++;
}
// Output number of characters in the line
System.out.println("Number of tokens = " + numberOfTokensGenerated);
// Output tokens
for (int counter = 0; counter < numberOfTokensGenerated; counter++) {
char character = file.toString().charAt(counter);
if (character == ' ') { System.out.println(); } else { System.out.print(character); }
}
} else {
System.out.println("File does not exist!");
System.exit(0);
}
System.out.println("\n");
}//end main
}//end class
When i run this code, this is what i get:
当我运行此代码时，这就是我得到的：
Please enter a java file name: D://eclipse-java-helios-SR1-win32/LexractData.DAT
Number of tokens = 129
java.io.FileReader@19821fException in thread "main" java.lang.StringIndexOutOfBoundsException: String index out of range: 25
at java.lang.String.charAt(Unknown Source)
at org.apache.lucene.analysis.StringProcessing.main(StringProcessing.java:40)
Please enter a java file name: D://eclipse-java-helios-SR1-win32/LexractData.DAT
Number of tokens = 129
java.io.FileReader@19821fException in thread "main" java.lang.StringIndexOutOfBoundsException: String index out of range: 25
at java.lang.String.charAt(Unknown Source)
at org.apache.lucene.analysis.StringProcessing.main(StringProcessing.java:40)
The input file will look like this:
输入文件将如下所示：
-K1 Account
--Op1 withdraw
---Param1 an
----Type Int
---Param2 amount
----Type Int
--Op2 deposit
---Param1 an
----Type Int
---Param2 Amount
----Type Int
--CA1 acNo
---Type Int
-K2 CheckAccount
--SC Account
--CA1 credit_limit
---Type Int
-K3 Customer
--CA1 name
---Type String
-K4 Transaction
--CA1 date
---Type Date
--CA2 time
---Type Time
-K5 CheckBook
-K6 Check
-K7 BalanceAccount
--SC Account
I just want to read the string which are starts with -K1, -K2, -K3, and so on... can anyone help me?
我只想阅读以-K1, -K2, -K3, 等开头的字符串……有人可以帮我吗？
回答by Kal
The problem is with this line --
问题出在这一行——
char character = file.toString().charAt(counter);
fileis a reference to a FileReaderthat does not implement toString().. it calls Object.toString()which prints a reference around 25 characters long. Thats why your exception says OutofBoundsException at the 26th character.
file是对FileReader未实现toString()..的引用，它调用Object.toString()打印大约 25 个字符长的引用。这就是为什么您的异常在第 26 个字符处说 OutofBoundsException 。
To read the file correctly, you should wrap your filereader with a bufferedreader and then put each readline into a stringbuffer.
要正确读取文件，您应该用一个缓冲读取器包装您的文件读取器，然后将每个读取行放入一个字符串缓冲区中。
FileReader fr = new FileReader(filename);
BufferedReader br = new BufferedReader(fr);
StringBuilder sb = new StringBuilder();
String s;
while((s = br.readLine()) != null) {
sb.append(s);
}
// Now use sb.toString() instead of file.toString()
// Now use sb.toString() instead of file.toString()
回答by lpreams
If you are wanting to tokenize the input file then the obvious choice is to use a Scanner. The Scanner class reads a given input stream, and can output either tokens or other scanned types (scanner.nextInt(), scanner.nextLine(), etc).
如果您想标记输入文件，那么显而易见的选择是使用扫描仪。Scanner 类读取给定的输入流，并可以输出标记或其他扫描类型（scanner.nextInt()、scanner.nextLine() 等）。
import java.util.Scanner;
import java.io.File;
import java.io.IOException;
public static void main(String[] args) throws IOException {
Scanner in = new Scanner(new File("filename.dat"));
while (in.hasNext) {
String s = in.next(); //get the next token in the file
// Now s contains a token from the file
}
}
Check out Oracle's documentation of the Scanner classfor more info.
查看Oracle 的 Scanner 类文档以获取更多信息。
