Summary of generic array creation in Java

In Java, you can declare a generic array , and you cannot create an array by directly using t[] tarr=new t[10] , and the simplest way is through array.newinstance (classtype,int Size) is the way to create an array such as the following program.

 Public classarraymaker<t> {
     
  PrivateClass<t> type;
       
 Public Arraymaker (class<t> type) {
this.type = type; 
  }      

@SuppressWarnings ("Unchecked")
 t[] Createarray (int size) {
return (t[]) array.newinstance (type, size); 
  } 

List<t> CreateList () {
   return NewArraylist<t> ();
}
         
 /**        * @paramargs*/    
     Public Static voidMain (string[] args) {
   /** Even though kind is stored as class<t>, erasure means the It is actually just being stored as a Class, with
* No parameter. So, if you don't some thing with it, as in creating an array, array.newinstance () doesn ' t
* Actually has the type information that ' s implied in kind; So it cannot produce the specific result, which
* Must therefore be cast, which produces a warning so you cannot satisfy.
    */       
Arraymaker<type> AM2 =NewArraymaker<type> (Type.class);
System.out.println (Arrays.aslist (Am2.createarray (10)));
System.out.println (Arrays.aslist (Am2.createlist ()));
}
}
   classType {
@Override
      PublicString toString () {
          return"Type";
}
}

Program One: This program mainly shows that in the use of generic arrays are prone to problems, because the book for the description of the program is more detailed, so only to reference the program.

Class Generic<t> {

}

Public class Arrayofgeneric {

public static void Main (string[] args) {

Generic<integer>[] Genarr;

Genarr = (generic<integer>[]) new generic[2];

System.out.println (Genarr);

}

}

Program Two: This program is mainly described in the execution of the program, the type information of the generic array will be erased, and in the course of the operation of the array type has and only object[], if we cast to the t[] type, although at compile time will not have an exception to produce, However, the runtime will have classcastexception thrown.

 Public classArrayofgeneric2<t> {         Publict[] TS;  PublicArrayOfGeneric2 (intsize) {TS= (t[])NewObject[size]; }            PublicT Get (intindex) {              returnTs[index]; }                 Publict[] Rep () {returnts; }                Public voidSetintindex, T t) {Ts[index]=T; }                Public Static voidMain (string[] args) {
Arrayofgeneric2<string> aog2 =NewArrayofgeneric2<string> (10); Object[] Objs=Aog2.rep ();            System.out.println (OBJS); /*Would throw classcastexception*/string[] STRs = Aog2.rep ();//system.out.println (STRs); }       }   

Program Three: The main description in the object by using object[] to save the data, the resulting object is that it can be held by the object is converted between T and object, but when the design to the array of conversion, still will be reported classcastexception

 Public classArrayofgeneric3<t>{object[] ts;  PublicARRAYOFGENERIC3 (intsize) {TS=NewObject[size]; }            PublicT Get (intindex) {            return(T) Ts[index]; }             Publict[] Rep () {return(t[]) TS; }             Public voidSetintindex, T t) {Ts[index]=T; }             Public Static voidMain (string[] args) {
Arrayofgeneric3<integer> aog2 =NewArrayofgeneric3<integer> (10); Object[] Objs=Aog2.rep ();  for(inti = 0; I < 10; i++) {Aog2.set (I, I);            System.out.println (Aog2.get (i)); } integer[] STRs=Aog2.rep ();        System.out.println (STRs); }    }   

Program Four: is a relatively perfect solution to a generic array

 Public classArrayofgeneric4<t>{t[] ts;  PublicARRAYOFGENERIC4 (class<t> type,intsize) {            /*To solution array of generic key code!*/TS=(t[]) array.newinstance (type, size); }              PublicT Get (intindex) {               returnTs[index]; }             Publict[] Rep () {returnts; }         Public voidSetintindex, T t) {Ts[index]=T; }          Public Static voidMain (string[] args) {
Arrayofgeneric4<integer> aog2 =NewArrayofgeneric4<integer> (Integer.class, 10); Object[] Objs=Aog2.rep ();  for(inti = 0; I < 10; i++) {Aog2.set (I, I);            System.out.println (Aog2.get (i)); }            Try{integer[] STRs=Aog2.rep (); System.out.println ("User array.newinstance to create generci of Array is successful!!!!!"); } Catch(Exception ex) {ex.printstacktrace (); }        }    }   

Please see the original http://developer.51cto.com/art/201202/317813.htm

Summary of generic array creation in Java