java - Why this piece of code isn't compilable -


here small piece of code , don't understand why javac can't compile it. miss? there errors?

public class helloworld<t> {     private static enum type {     }      private t value;     private list<type> types = new arraylist<>();      public t getvalue() { return value; }      public list<type> gettypes() { return types; }      public static void main( string[] args ) {         ( type type : new helloworld().gettypes() ) { // error: type mismatch: cannot convert element type object helloworld.type          }     } }

why gettypes() returning object (raw) list when should type list?

link online compiler

this looks compiler limitation me. gettypes returns list<type>, using raw helloworld type should make no difference.

that said, either of these 2 solutions overcome error :

  1. create parameterized type of helloworld instead of raw type :

    for (type type : new helloworld<integer>().gettypes() ) { // type do, chose                                                            // integer arbitrarily show                                                           // doesn't matter  }

  2. use local variable store list before using :

    list<type> types = new helloworld().gettypes(); (type type : types) {   }

anyway, parameterized types should preferred on raw types, i'll use first solution (with whatever type parameter makes sense in class).


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