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GenericTest3.java
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29 lines (27 loc) · 1014 Bytes
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package code;
class Apple2<T extends Number>{
T size;
public Apple2(){}
public Apple2(T size){
this.size = size;
}
public void setSize(T size){
this.size = size;
}
public T getSize(){
return this.size;
}
}
public class GenericTest3{
public static void main(String[] args) {
Apple2<Integer> a = new Apple2<>(6);
Integer as = a.getSize();
Apple2 b = a; //泛型擦粗，当把一个带泛型信息的变量赋值给一个不带泛型信息的变量时，泛型信息会被擦除，默认是声明该泛型形参时的上限类型
Number bs = b.getSize();
System.out.println(bs);
// Integer bs2 = b.getSize(); //此时会报错，泛型信息被擦除，因此bs类型应为Number
Apple2<Integer> c = b; //泛型转换，这里b实际上引用的还是Apple2<Integer>类型，因此这里c也应该是Apple2<Integer>类型
Integer cs = c.getSize();
System.out.println(cs);
}
}