41 lines
1.1 KiB
Java
41 lines
1.1 KiB
Java
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//: generics/UnboundedWildcards1.java
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import java.util.*;
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public class UnboundedWildcards1 {
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static List list1;
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static List<?> list2;
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static List<? extends Object> list3;
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static void assign1(List list) {
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list1 = list;
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list2 = list;
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// list3 = list; // Warning: unchecked conversion
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// Found: List, Required: List<? extends Object>
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}
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static void assign2(List<?> list) {
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list1 = list;
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list2 = list;
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list3 = list;
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}
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static void assign3(List<? extends Object> list) {
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list1 = list;
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list2 = list;
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list3 = list;
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}
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public static void main(String[] args) {
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assign1(new ArrayList());
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assign2(new ArrayList());
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// assign3(new ArrayList()); // Warning:
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// Unchecked conversion. Found: ArrayList
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// Required: List<? extends Object>
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assign1(new ArrayList<String>());
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assign2(new ArrayList<String>());
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assign3(new ArrayList<String>());
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// Both forms are acceptable as List<?>:
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List<?> wildList = new ArrayList();
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wildList = new ArrayList<String>();
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assign1(wildList);
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assign2(wildList);
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assign3(wildList);
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}
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} ///:~
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