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  1.  
  2. import java.util.List;
  3.  
  4. import java.util.ArrayList;
  5.  
  6.  
  7.  
  8.  
  9. public class Main {
  10.  
  11.  
  12.     public static void main(String[] args) {
  13.  
  14.         // test addLot
  15.         {
  16.             List<Asset> assets = new ArrayList<Asset>();
  17.             addLot(assets);
  18.  
  19.             List<Lot> lots = new ArrayList<Lot>();
  20.             addLot(lots);
  21.  
  22.             List<CommercialLot> commercialLots = new ArrayList<CommercialLot>();
  23.             // you cannot do this, compile-time error:
  24.             // addLot(commercialLots);
  25.         }
  26.  
  27.         // test addCommercialLot
  28.         {
  29.             List<Asset> assets = new ArrayList<Asset>();
  30.             addCommercialLot(assets);
  31.  
  32.             List<Lot> lots = new ArrayList<Lot>();
  33.             addCommercialLot(lots);
  34.  
  35.             List<CommercialLot> commercialLots = new ArrayList<CommercialLot>();
  36.             addCommercialLot(commercialLots);
  37.         }
  38.  
  39.     }
  40.  
  41.     public static void addLot(List<? super Lot> lots) {
  42.  
  43.         // you cannot do this, compile-time error:
  44.         // lots.add(new Asset());
  45.  
  46.         // you can do this:
  47.         lots.add(new Lot());
  48.  
  49.         // and so is this
  50.         lots.add(new CommercialLot());
  51.  
  52.         ////////
  53.  
  54.         for(Asset a : (List<Asset>) lots) {
  55.         }
  56.  
  57.         for(Lot l : (List<Lot>) lots) {
  58.         }
  59.  
  60.         // you cannot do this, compile-time error:
  61.         /*for(CommercialLot c : (List<CommercialLot>) lots) {
  62.         } */
  63.     }
  64.  
  65.     public static void addCommercialLot(List<? super CommercialLot> commercialLots) {
  66.  
  67.         // you cannot do this, compile-time error:
  68.         // commercialLots.add(new Asset());
  69.  
  70.         // you cannot do this, compile-time error:
  71.         // commercialLots.add(new Lot());
  72.  
  73.         // but of course, you can do this:
  74.         commercialLots.add(new CommercialLot());
  75.  
  76.         ////////
  77.  
  78.         for(Asset a : (List<Asset>) commercialLots) {
  79.         }
  80.  
  81.         for(Lot l : (List<Lot>) commercialLots) {
  82.         }
  83.  
  84.         for(CommercialLot c : (List<CommercialLot>) commercialLots) {
  85.         }
  86.     }
  87. }
  88.  
  89. class Asset {
  90. }
  91.  
  92. class Lot extends Asset  {
  93. }
  94.  
  95. class CommercialLot extends Lot {
  96. }
  97.  
  98.  
Success #stdin #stdout 0.03s 245632KB
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https://ideone.com/dbgCU
language:
Java (HotSpot 12)
created:
11 years ago
visibility:
public

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