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Java 8 ConcurrentHashMap.keySet() bytecode incompatibility
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// In Java 8, ConcurrentHashMap backward compatibility was broken by changing to a covariant return type | |
Code: | |
0: aload_0 | |
1: invokespecial #1 // Method java/lang/Object."<init>":()V | |
4: return | |
public static void main(java.lang.String...); | |
Code: | |
0: new #2 // class java/util/TreeSet | |
3: dup | |
4: invokespecial #3 // Method java/util/TreeSet."<init>":()V | |
7: new #4 // class java/util/concurrent/ConcurrentHashMap | |
10: dup | |
11: invokespecial #5 // Method java/util/concurrent/ConcurrentHashMap."<init>":()V | |
14: invokevirtual #6 // Method java/util/concurrent/ConcurrentHashMap.keySet:()Ljava/util/concurrent/ConcurrentHashMap$KeySetView; | |
17: invokevirtual #7 // Method java/util/TreeSet.addAll:(Ljava/util/Collection;)Z | |
20: pop | |
21: return |
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While Java 8 typically does a good job of creating bytecode that is compatible with Java 7, this is an example of where it does not.