how do I extract Name and Value from a line of text while reading from a file using Java?

Question

A file name will be passed in from standard in. I want to open it, read it, and create some information based off the text in the file.

For example, if this is a line in the file:

Hristo 3

... then I want to create a Member() named Hristo with a value of 3. So I want to pull out a String for the name and an int for the value. The name and the value are separated by some unknown number of tabs and spaces which I need to ignore. Could I just read the line, use .trim() to get rid of whitespace, and the last character would be the value?

I have not shown the class Member() for simplicity's sake. This is what I have so far:

public static void main(String[] args) {

    int numMembers = 0;
    ArrayList<Member> veteranMembers = new ArrayList<Member>();

    File file = new File(args[0]);
    FileReader fr;
    BufferedReader br;

    // attempt to open and read file
    try {
        fr = new FileReader(file);
        br = new BufferedReader(fr);

        String line;

        // read file
        while ((line = br.readLine()) != null) {

                // extract name and value from line
                ... ? ...

                // create member
                // initialize name and value
                Member member = new Member();
                veteranMembers.add(member);
        }
        br.close();

    } catch (FileNotFoundException e1) {
        // Unable to find file.
        e1.printStackTrace();
    } catch (IOException e) {
        // Unable to read line.
        e.printStackTrace();
    }
}

How would I parse that line of text?

Thanks in advance for your help.

Answer 1

I would use the split function. You can give it a regular expression as the argument ie

line.split(" |\t");

will return array of the words ( {list[0] = Hristo, list[1] = 3} in your example) Hope it helps.

Answer 2

使用split("\\\\s+") ，此正则表达式忽略字符串中的任何空格，制表符等。

Answer 3

A more robust way might be to use regular expressions; if you received malformed input (eg, "Ted One"), parseInt() would throw a NumberFormatException.

import java.util.regex.*;

...

Pattern p = Pattern.compile("^(.*)\\s+(\\d+)$"); // Create a regex Pattern that only matches (text - white space - integer)
Matcher m = p.matcher(line); // Create a Matcher to test the input line
if(m.find()){
      // If there's a match, ..
    String name = m.group(1); // Set "name" to the first parenthesized group
    String value = m.group(2); // Set "value" to the second parenthesized group
}
else{
      // Bad Input
}

Answer 4

Looks like a home work. You came really close doing it. Use StringTokenizer to tokenize the line . Then create a new member object and and call setters for both the attributes with tokens as params. If your second attribute is an int use parseInt to convert and assign it.