Java – cast to inner classes using generics
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Java
Consider the following codes:
public class Outer<T> { public class Inner{ } public static <T> Outer<T>.Inner get(){ Object o = new Object(); return (Outer<T>.Inner)o; } public static void main(String[] args) throws Exception { Outer.<String>get(); } }
This code was successfully compiled in eclipse, but could not be compiled in javac:
Outer.java:10: ')' expected return (Outer<T>.Inner)o; ^ Outer.java:10: ';' expected return (Outer<T>.Inner)o; ^ Outer.java:10: illegal start of expression return (Outer<T>.Inner)o; ^ 3 errors
Is this an error in javac or eclipse?
If I change the transformation to (outer. Inner) O, it compiles, despite a warning:
Solar eclipse:
Outer.Inner is a raw type. References to generic type Outer<T>.Inner should be parameterized
Javac:
Outer.java:10: warning: [unchecked] unchecked conversion found : Outer.Inner required: Outer<T>.Inner return (Outer.Inner)o; ^ 1 warning
Javac version: 1.6 0_ twenty-one
Solution
I found that this was an error in the javac compiler and later fixed it JDK 7b100 compiles this fine
see http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=6665356
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