wildcard generics

bashvar goodData = new ArrayList();goodData.add(new GoodData(1));goodData.add(new GoodData(2));ArrayList wildGoodData = goodData;wildGoodData.add(new BasicData()); // 编译报错，根本不知道是哪个子类型wildGoodData.add(new GoodData(3)); // 编译报错，根本不知道是哪个子类型wildGoodData.add(new VeryGoodData(3)); // 编译报错，根本不知道是哪个子类型GoodData g = wildGoodData.get(0); //OKArrayList wildSuperBasicData = new ArrayList(); //OKArrayList bbb = wildSuperBasicData; //编译报错wildSuperBasicData.add(new BasicData()); // 编译报错，根本不知道是哪个父类型wildSuperBasicData.add(new GoodData(1)); //OK,类型匹配wildSuperBasicData.add(new VeryGoodData(3)); //OK，类型匹配BasicData b = wildSuperBasicData.get(0); //编译报错,只能用object接受Object bb = wildSuperBasicData.get(0); //okvar goodDataForPredicate = new ArrayList();Predicate p  = d -> d.data == 1;goodDataForPredicate.removeIf(p); //OKPredicate p1  = d -> d.data == 1;goodDataForPredicate.removeIf(p1); //OKPredicate p2  = d -> d.data == 1;goodDataForPredicate.removeIf(p2); //类型错误

VeryGoodData extends GoodData extends BasicData

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