Why IDEA shows that “Type parameter 'T' cannot be instantiated directly”. What I want to do is declare a generic array

Asked Sep 06 '21 at 12:29

Active Sep 06 '21 at 12:40

Viewed 2,985 times

the code is below:

package linear_list;

public class SeqList<T> {
    protected int n;        
    protected T[] element;
    private static final int MIN_CAPACITY=16;
    public SeqList(int length){
        if (length<MIN_CAPACITY)
            length=MIN_CAPACITY;
        this.element=new T[length];   //this row is reported an error
        this.n=0;
    }
}

Why IDEA shows that “Type parameter 'T' cannot be instantiated directly”. What I want to do is declare a generic array.

asked Sep 06 '21 at 12:29

Frederick_Chen

Generic are for compile time type safety, so if you initialize generic variable it should know the type of object at compile time. So generic type object can not be initialized this way. Rather you would need to take this as input from user. – Gaurav Jeswani Sep 06 '21 at 12:35
1

Does this answer your question? [What's the reason I can't create generic array types in Java?](https://stackoverflow.com/questions/2927391/whats-the-reason-i-cant-create-generic-array-types-in-java) – maloomeister Sep 06 '21 at 12:35
You can do something like this `T newT = (T[]) element.getClass().newInstance()` – Maneesha Indrachapa Sep 06 '21 at 12:40
1

@ManeeshaIndrachapa you can't do that until `element` is initialized. – Andy Turner Sep 06 '21 at 12:41
@maloomeister Yes – Frederick_Chen Sep 06 '21 at 12:53
Just cast an object array. `(T[]) new Object[10];` – Michael Sep 06 '21 at 13:24

Why IDEA shows that “Type parameter 'T' cannot be instantiated directly”. What I want to do is declare a generic array

0 Answers0