37 lines
1.1 KiB
Java
37 lines
1.1 KiB
Java
// collections/AsListInference.java
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// (c)2016 MindView LLC: see Copyright.txt
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// We make no guarantees that this code is fit for any purpose.
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// Visit http://mindviewinc.com/Books/OnJava/ for more book information.
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// Arrays.asList() makes its best guess about type.
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import java.util.*;
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class Snow {}
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class Powder extends Snow {}
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class Light extends Powder {}
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class Heavy extends Powder {}
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class Crusty extends Snow {}
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class Slush extends Snow {}
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public class AsListInference {
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public static void main(String[] args) {
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List<Snow> snow1 = Arrays.asList(
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new Crusty(), new Slush(), new Powder());
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// Won't compile:
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// List<Snow> snow2 = Arrays.asList(
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// new Light(), new Heavy());
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// Compiler says:
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// found : java.util.List<Powder>
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// required: java.util.List<Snow>
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// Collections.addAll() doesn't get confused:
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List<Snow> snow3 = new ArrayList<>();
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Collections.addAll(snow3, new Light(), new Heavy());
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// Give a hint using an
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// explicit type argument specification:
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List<Snow> snow4 = Arrays.<Snow>asList(
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new Light(), new Heavy());
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}
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}
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