25 lines
706 B
Java
25 lines
706 B
Java
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//: generics/GenericWriting.java
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import java.util.*;
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public class GenericWriting {
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static <T> void writeExact(List<T> list, T item) {
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list.add(item);
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}
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static List<Apple> apples = new ArrayList<Apple>();
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static List<Fruit> fruit = new ArrayList<Fruit>();
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static void f1() {
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writeExact(apples, new Apple());
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// writeExact(fruit, new Apple()); // Error:
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// Incompatible types: found Fruit, required Apple
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}
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static <T> void
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writeWithWildcard(List<? super T> list, T item) {
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list.add(item);
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}
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static void f2() {
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writeWithWildcard(apples, new Apple());
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writeWithWildcard(fruit, new Apple());
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}
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public static void main(String[] args) { f1(); f2(); }
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} ///:~
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