java - Ideone Java 程序运行时错误

Question

/* package whatever; // don't place package name! */

import java.util.*;
import java.lang.*;
import java.io.*;

/* Name of the class has to be "Main" only if the class is public. */

class time
{
    int h,m,sec;
    void getdata()throws IOException
    { /*Scanner in = new Scanner(System.in);`
      h=in.nextInt();
      m= in.nextInt();
      s=in.nextInt();*/
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));

        String s= br.readLine();
        String str[] = s.split(" ");

        h=Integer.parseInt(str[0]);
        m=Integer.parseInt(str[1]);
        sec=Integer.parseInt(str[2]);
    }
    int calc_time(time t1,time t2)
    { return ((t2.h - t1.h)*3600 + (t2.m - t1.m)*60 + (t2.sec - t1.sec));
    }
    public static void main (String[] args) throws java.lang.Exception
    {
        // your code goes here
        time t = new time();
        t.getdata();
        time te = new time();
        te.getdata();
        time tt = new time();
        int val = tt.calc_time(t,te);
        if(val>=0&&val<=99) System.out.println("S");
        else if(val>99&&val<=199) System.out.println("C");
        else if(val>199 && val<=299) System.out.println("S");
        else if(val>299 && val<=399) System.out.println("C");

    }
}

尽管这个特定程序在我的电脑上运行良好，但我在 Ideone 上遇到了运行时错误。它指示第二个对象的 split 函数和 getdata() 函数调用出现错误。

Answer 1

http://ideone.com/qpOO9R

已到达 STDIN 流的末尾，这意味着运行以下命令后:

  String s = br.readLine();

s 仍然为 null，这会导致以下行出现 NPE:

String str[] = s.split(" ");

要解决此问题，请检查 null 并执行一些合理的操作，并提供一些输入供 Ideone 使用。此外，您的 BufferedReader 每次执行时只应创建一次，如以下 ideone 草图所示:http://ideone.com/VtQrxk

相关javadoc:

public String readLine() throws IOException

Reads a line of text. A line is considered to be terminated by any one of a line feed ('\n'), a carriage return ('\r'), or a carriage return followed immediately by a linefeed.

Returns:

A String containing the contents of the line, not including any line-termination characters, or null if the end of the stream has been reached

http://docs.oracle.com/javase/7/docs/api/java/io/BufferedReader.html#readLine()