java - "Cannot instantiate the type..."

Question

当我尝试运行这段代码时:

import java.io.*;
import java.util.*;

public class TwoColor
{
    public static void main(String[] args) 
    {
         Queue<Edge> theQueue = new Queue<Edge>();
    }

    public class Edge
    {
        //u and v are the vertices that make up this edge.
        private int u;
        private int v;

        //Constructor method
        public Edge(int newu, int newv)
        {
            u = newu;
            v = newv;
        }
    }
}

我收到此错误:

Exception in thread "main" java.lang.Error: Unresolved compilation problem:     Cannot instantiate the type Queue    at TwoColor.main(TwoColor.java:8)

我不明白为什么我不能实例化这个类...这对我来说似乎是正确的...

Answer 1

java.util.Queue 是一个接口(interface)，所以你不能直接实例化它。你可以实例化一个具体的子类，比如LinkedList:

Queue<T> q = new LinkedList<T>;