Question

import java.io.BufferedReader;
import java.io.DataInputStream;
import java.io.FileInputStream;
import java.io.InputStreamReader;

    public class extractvalues {
        @SuppressWarnings("null")
        public static void main(String [] args)
        {       
            try{
                // command line parameter
                FileInputStream fstream = new  FileInputStream("c:/kdd.txt");

                // Get the object of DataInputStream
                DataInputStream in = new DataInputStream(fstream);
                //to Read values 
                BufferedReader br = new BufferedReader(new InputStreamReader(in));
                String strLine;


                //Read File Line By Line
                while ((strLine = br.readLine()) != null)  
                {
                    System.out.println(strLine);
                    String[] splitted=null;     
                    //split the given line into array of words seperated by comma               
                    splitted=strLine.split(",");

                    int i=0;
                    //continue loop till it find "." since everyline contain "." in the end 
                    while(!".".equals(splitted)) 
                    {  
                       //print each string one by one                                                    
                       System.out.println(splitted[i++]);                                  
                    }

                }

                //Close the input stream
                in.close();
            }
            catch (Exception e)
            {//Catch exception if any
               System.err.println("Error: " + e.getMessage());
            }
        }

    }

我在循环中运行2。第一个循环将从.txt文件中逐行读取，第二个循环将从行读取每个字符串。但是当我运行循环时它会读取第一行和字符串然后停止。我不知道我到达的地方错了。我错过了一些请帮忙！

Answer 1

将内部while循环更改为：

//Read File Line By Line
while ((strLine = br.readLine()) != null) {
    System.out.println(strLine);
    String[] splitted=null;     

    //split the given line into array of words seperated by comma               
    splitted=strLine.split(",");

    for (int i=0; i < splitted.length; ++i ) {
        if (splitted[i].equals("."))
            break;

        //print each string one by one                                                    
        System.out.println(splitted[i]);
    }
}

您正在引用整个数组splitted，而不是访问数组中的元素，后者是您实际想要执行的操作。

Answer 2

在我的本地计算机上运行你的代码并在此行获得异常 - ArrayIndexOutOfBounds

  System.out.println(splitted[i++]);

Answer 3

问题是拆分是String#Array，你无法使用equals()方法比较这样的数组

 while(!".".equals(splitted))   ---> This is logically incorrect way !!

因此，请尝试forEach循环并将数组中的每个字符串与.

进行比较

for(String temp:splitted){
     if(temp.equals("."))  <-- Using equals for comparing 2 String
        break;
   System.out.println(temp);
}

Answer 4

将内部while循环更改为此，并确保不需要

if (splitted[i].equals("."))

因为字符串数组的最后一个索引不仅有（。），所以它也有额外的字符。

while ((strLine = br.readLine()) != null){
System.out.println(strLine);
String[] splitted=null;     
//split the given line into array of words seperated by comma               
splitted=strLine.split(",");
//continue loop till it find "." since everyline contain "." in the end 
for(int i=0;i<splitted.length;i++) 
{  
System.out.println(splitted[i++]);                                  
}
}

外循环运行一次？

4 个答案: