错误：<identifier> 制作 generics 数组时预期</identifier>

Question

I am trying to create an array of generics by type casting, but everything I've tried has resulted in error: <identifier> expected . The task is to make an array based Deque. I've tried:

• @suppresswarning("unchecked")
• Random rewriting of the code

Here is a snippet of the code

public class dequeCyclic<E> implements Deque<E> {
private int first;
private int last; 
private E[] deque;

public dequeCyclic(int size){
    @SuppressWarning("unchecked")
    deque =(E[]) new Object[size];
    first = -1; 
    last = -1; 
}   

Any help would be greatly appreciated.

Answer 1

You can't put @SuppressWarning on statements. They are only allowed on declarations, so you have three options, either annotate the class:

@SuppressWarning("unchecked")
public class dequeCyclic<E> implements Deque<E> {

or the constructor:

@SuppressWarning("unchecked")
public dequeCyclic(int size) {
    deque =(E[]) new Object[size];
    first = -1; 
    last = -1; 
}

Or create a local temporary variable:

public dequeCyclic(int size) {
    @SuppressWarning("unchecked")
    E[] temp =(E[]) new Object[size];
    deque = temp;
    first = -1; 
    last = -1; 
}

The last one with the temporary variable should be prefered, because the first and second variant suppress all unchecked warnings inside of them. Which is generally more harmful than useful.