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  1.     /* package whatever; // don't place package name! */
  2.  
  3.     import java.io.*;
  4.     import java.lang.*;
  5.     import java.util.*;
  6.  
  7.     /* Name of the class has to be "Main" only if the class is public. */
  8.     class Ideone {
  9.       interface Tapelibrary<T extends TapeDrive> {
  10.         List<T> getListofDrives();
  11.  
  12.         void doSomethingWithDrive(T d);
  13.       }
  14.  
  15.       static class SpecificTapeLibrary implements Tapelibrary<HPDrive> {
  16.         private List<HPDrive> driveList;
  17.  
  18.         SpecificTapeLibrary() {
  19.           driveList.add(new HPDrive());
  20.           driveList.add(new HPDrive());
  21.           driveList.add(new HPDrive());
  22.         }
  23.  
  24.         @Override
  25.         public List<HPDrive> getListofDrives() {
  26.           return driveList;
  27.         }
  28.  
  29.         @Override
  30.         public void doSomethingWithDrive(HPDrive d) {
  31.           d.doSomethingHPspecific();
  32.         }
  33.       }
  34.  
  35.       abstract static class TapeDrive {
  36.         void doSomething() {}
  37.       }
  38.  
  39.       static class HPDrive extends TapeDrive {
  40.         void doSomethingHPspecific() {}
  41.       }
  42.  
  43.       static <T extends TapeDrive> void doStuff(Tapelibrary<T> t) {
  44.         if (t == null) return;
  45.  
  46.         List<T> listOfDrives = t.getListofDrives();
  47.  
  48.         // the user selects a drive by using a small UI or something
  49.         T selectedDrive = listOfDrives.get(0);
  50.  
  51.         t.doSomethingWithDrive(selectedDrive);
  52.       }
  53.  
  54.       public static void main(String[] args) throws java.lang.Exception {
  55.         Tapelibrary<? extends TapeDrive> t = null;
  56.         doStuff(t);
  57.       }
  58.     }
Success #stdin #stdout 0.03s 711168KB
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https://ideone.com/k43QXx
language:
Java (12.0.1)
created:
7 years ago
visibility:
public

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