帮助：如何计算JAVA中的行数？ [英] Help: How to Count number of lines in JAVA?

问题描述

你好其他程序员，我有一个问题：编写一个静态方法，Display（）接受表示文件名的字符串。该方法应该只读取并显示文件内容的前五行。如果文件包含少于5行，则应显示文件的全部内容。



（假设我已完成所有必要的导入）这是我的尝试：

 public static void Display（String filename）throws IOException 
 {
 File file = new File（filename）; 
 Scanner read = new Scanner（file）; 
 
 while（read.hasNext（））
 {
 //到目前为止我已经尝试过这个
 int count = 0; 
 String lineReader = read.nextLine（）; 
 count ++; 
 
 if（count< 5）
 {
 System.out.println（lineReader）; 
} 
} 
 
 read.close（）; 
 
} 

解决方案

使用 java.util.Scanner 只是计算行数大矫枉过正！但是，你很亲密。声明一些整数计数器变量，在循环之前初始化为0，并在每次成功找到下一行时递增。



如果没有这样的过度杀伤，请使用 java.io.BufferedReader 和 java.io.BufferedReader.readLine ：

http://docs.oracle.com/javase/1.5.0/docs/api/java/io/ BufferedReader.html [ ^ ]，

http://docs.oracle.com/javase/1.5.0/docs/api/java/io/BufferedReader.html#readLine%28%29 [ ^ ]。

-SA

  public   static   void 显示（< span class =code-sdkkeyword> String  filename） throws  IOException 
 {
 
  int  lineCounter = 1; 
 
文件file =  new 文件（文件名）; 
扫描仪读取= 新扫描仪（文件）; 
 
  while （read.hasNext（）&& lineCounter< = 5）
 {
 
  String  lineReader = read.nextLine（）; 
 System.out.println（lineReader）; 
 lineCounter ++; 
 
} 
 
 read.close（）; 
 
} 

[edit]已添加代码块[/ edit]

Hello there fellow programmers, I have a question: Write a static method, Display() that accepts a string representing the name of the file. The method should read and display only the first the five lines of the file''s contents. If the file contains less than 5 lines, it should display the file''s entire contents.

(Assuming that I made all the necessary imports) Here is my attempt:

public static void Display (String filename) throws IOException
{
   File file = new File (filename);
   Scanner read = new Scanner (file);

   while (read.hasNext())
   {
//So far I have tried this
       int count=0;
       String lineReader = read.nextLine();
       count++;

      if (count <5)
      {
        System.out.println(lineReader);
      }
   }
   
   read.close();

}

解决方案

Using java.util.Scanner just for counting lines is a big overkill! However, you are close. Declare some integer counter variable, initialize to 0 before the loop and increment each time you successfully find next line.

Without such an overkill, use java.io.BufferedReader and java.io.BufferedReader.readLine:
http://docs.oracle.com/javase/1.5.0/docs/api/java/io/BufferedReader.html[^],
http://docs.oracle.com/javase/1.5.0/docs/api/java/io/BufferedReader.html#readLine%28%29[^].

—SA

public static void Display (String filename) throws IOException
{ 

   int lineCounter=1;

   File file = new File (filename);
   Scanner read = new Scanner (file);
 
   while (read.hasNext() && lineCounter<=5 )
   {

       String lineReader = read.nextLine();
        System.out.println(lineReader);
        lineCounter++;
      
   }
   
   read.close();
 
}

[edit]Code block added[/edit]

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