User Tools

Site Tools


evolving_java-based_apis

Differences

This shows you the differences between two versions of the page.

Link to this comparison view

Both sides previous revision Previous revision
Next revision
Previous revision
evolving_java-based_apis [2014/02/06 08:00]
yann
evolving_java-based_apis [2017/09/06 01:54] (current)
Line 61: Line 61:
 Also, the document provides the simplest, clearest explanation of Java 1.5+ type erasure mechanism, that I reproduce here for the sake of beauty: Also, the document provides the simplest, clearest explanation of Java 1.5+ type erasure mechanism, that I reproduce here for the sake of beauty:
  
-"A raw type is a use of a generic type without the normal type arguments. For example, "​List"​ in the declaration statement "List x = null;" is a raw type since List is a generic type declared "​public interface List<​E>​ ..." in JDK 1.5. Contrast this to a normal use of List which looks like "​List<​String>​ x = null;" or "​List<?>​ x = null;" where a type augument ("​String"​) or wildcard is specified. +>A raw type is a use of a generic type without the normal type arguments. For example, "​List"​ in the declaration statement "List x = null;" is a raw type since List is a generic type declared "​public interface List<​E>​ ..." in JDK 1.5. Contrast this to a normal use of List which looks like "​List<​String>​ x = null;" or "​List<?>​ x = null;" where a type augument ("​String"​) or wildcard is specified.  
- +>> ​ 
-> The term erasure is suggestive. Imagine going through your code and literally erasing the type parameters from the generic type declaration (e.g., erasing the "<​E>"​ in "​public interface List<​E>​ ...") to get a non-generic type declaration,​ and replacing all occurrence of the deleted type variable with Object. For type parameters with type bounds (e.g., "<E extends T1 & T2 & T3 & ...>"​),​ the leftmost type bound ("​T1"​),​ rather than Object, is substituted for the type variable. The resulting declaration is known as the erasure."​+>> The term erasure is suggestive. Imagine going through your code and literally erasing the type parameters from the generic type declaration (e.g., erasing the "<​E>"​ in "​public interface List<​E>​ ...") to get a non-generic type declaration,​ and replacing all occurrence of the deleted type variable with Object. For type parameters with type bounds (e.g., "<E extends T1 & T2 & T3 & ...>"​),​ the leftmost type bound ("​T1"​),​ rather than Object, is substituted for the type variable. The resulting declaration is known as the erasure."​
evolving_java-based_apis.1391673615.txt.gz · Last modified: 2017/09/06 01:54 (external edit)