尝试将文件中的字符串解析为int。 获取NumberFormatException：对于输入字符串“”，eaven字符串似乎是一个很好的int字符串。 爪哇

Question

I have been trying to figure this out for couple of hours now and I hope one of you can help me. I have an file (actually two but thats not important) that have some rows and columns with numbers and blank spaces between. And I'm trying to read those with BufferedReader. And that works great. I can print out the strings & chars however I want. But when I try to parse those strings and chars I get the following error:

Exception in thread "main" java.lang.NumberFormatException: For input string: ""
at java.lang.NumberFormatException.forInputString(Unknown Source)
at java.lang.Integer.parseInt(Unknown Source)
at java.lang.Integer.parseInt(Unknown Source)
at FileProcess.processed(FileProcess.java:30)
at DecisionTree.main(DecisionTree.java:16)

From what I have found with google I think the error is located in how I read my file.

public class ReadFiles {
private BufferedReader read;
public ReadFiles(BufferedReader startRead) {
    read = startRead; 
}

public String readFiles() throws IOException {
    try {
        String readLine = read.readLine().trim();
        String readStuff = "";
        while(readLine != null) {
            readStuff += (readLine + "\n");
            readLine = read.readLine();
        }
            return readStuff;
    }
    catch(NumberFormatException e) {
        return null;
    }
}

And for the parsing bit

public class FileProcess {

public String processed() throws IOException {
fileSelect fs = new fileSelect();
ReadFiles tr = new ReadFiles(fs.traning());
String training = tr.readFiles();   

ReadFiles ts = new ReadFiles(fs.test());
String test = ts.readFiles();
List liste = new List(14,test.length());

String[] test2 = test.split("\n");

for(int i = 0; i<test2[0].length(); i++) {      
    char tmp = test.charAt(i);
    String S = Character.toString(tmp).trim();

    //int i1 = Integer.parseInt(S);

    System.out.print(S);        
}

This isn't the actual code for what I planning to do with the output, but the error appears at the code that is commented out. So my string output is as following:

12112211

Which seems good to parse to integer. But it does not work. I tried to manually see what's in the char position 0 and 1, for 0 I get 1, but for 1 I get nothing aka "" . So how can I remove the "" ? I hope you guys can help me out, and let me know if you need more info. But I think I have covered what's needed.

Thanks in advance :)

Yeah, and another thing: If I replace "" with "0" it works, but then I get all those zeros which I can't find a clever way to remove. But is it possible to maybe skip them while parsing or something? My files only hold 1 and 2, so it wouldn't interfere with anything if it is possible.

Answer 1

如果您有两个相邻的分割字符（即\\ n \\ n），或者如果在trim（）调用中传递了空格字符，则将返回字符串“”，因此请忽略空字符串并继续。

Answer 2

You could use the Scanner class to parse for ints, skipping Whitespace:

sc = new java.util.Scanner (line);
sc.nextInt ();

Another idea is to trim the line, split, and parse the parts:

lin = line.trim ();
String [] words = lin.split (" +");
for (String si : words) 
    Integer.parseInt (si);