Question

当我在另一个提供错误的类中使用文件对象时。在java中有任何机制我们可以在另一个类中使用对象。

class Abc {
    File file = new File("D:\\test.txt");
    BufferedReader br = new BufferedReader(new FileReader(alert_file));
}

class Def {
    File f_rename = new File("D:\\result.txt");
    if (file.renameTo(f_rename)) {
        System.out.println("file has been renamed");
    } else {
        System.out.println("file not renamed");
    }
}

Answer 1

您编写的类只是首先需要实例化的模板。这里你要做的是访问ABC类中定义的变量到类Def，直到你在Def对象中有ABC类的对象时才允许这样做。以下代码演示了如何完成：

class MyClass{
     File file;
     public MyClass(){
        file=new File("somefile.txt");
     }
     //in some method you can write...
     public void someMethod(){
        SomeOtherClass soc=new SomeOtherClass(file);
        soc.someOtherMethod();
     }
} 

   class SomeOtherClass{
      File file; 
      public SomeOtherClass(File file){
        this.file=file;
      }
      public someOtherMethod(){
        //do whatever you want here with file object
      }
   }

Answer 2

您编写的代码片段错误，

班级Abc {

public void checkFile（）{

File file = new File("D:\\test.txt");
BufferedReader br = new BufferedReader(new FileReader(alert_file));

}

class Def {

public void checkFile（） {

File f_rename = new File("D:\\result.txt");
if (file.renameTo(f_rename)) {
    System.out.println("file has been renamed");
} else {
    System.out.println("file not renamed");
}

}

你可以通过不同的方式实现，

静态变量。
实例化obj＆amp;吸气方法。

Answer 3

class Abc 
{
public static void main(String[] ars)
{
File file = new File("D:\\test.txt");
BufferedReader br = new BufferedReader(new FileReader(alert_file));
Def d=new Def();    
d.rename();
}
}

class Def {
public static void rename()
{
File f_rename = new File("D:\\result.txt");
if (Abc.file.renameTo(f_rename)) 
{
System.out.println("file has been renamed");
} 
else 
{
System.out.println("file not renamed");
}
}
}

我如何在另一个类中使用一个文件对象

3 个答案: