读取一次文件并多次使用这些数据 [英] Read the file once and use the data multiple times

问题描述

我写了一个java类，它读取一个文件，并将每行存储在一个数组列表中。我想大量访问这个数组列表。每次调用该类访问数组列表时，都会再次读取该文件。我希望文件被读取一次，然后多次访问数组列表。我怎么做到这一点？

解决方案

将其存储在类的字段中。即：

  public class Foo {
 private List< String>列表; 
 
公开列表< String> readData（）{
 if（list！= null）{
 return list; 
} 
 //读取数据。 
 
 
 
 
 
 
 
请注意，如果在多线程环境中使用它必须采取额外的措施。例如，在方法中放置 synchronized 。
正如Peter指出的，如果你可以读取多个文件，那么你可以使用 Map< String，List< String>>  
 
 
 
另外需要注意的是，这个班如果您创建了多个实例，则不会达到所需的效果。
 
I wrote a java class which reads a file and stores each line in an arraylist. I want to access this arraylist large number of times. Everytime the class is called to access the arraylist, it reads the file again. I want the file to be read once and then access the arraylist multiple times. How can I do this?
解决方案
Store it in a field of the class. I.e.:
public class Foo {
   private List<String> list;

   public List<String> readData() {
       if (list != null) { 
           return list;
       }
       // do the reading.
   }
}
Note that if this is used in a multithreaded environment you'd have to take extra measures. For example put synchronized on the method.

As Peter noted, if you can read multiple files, then you can use a Map<String, List<String>>

Another note is that you should use only one instance of this class. If you create multiple instances you won't have the desired effect.

                        
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