Question

此代码用于学习泛型类和堆栈操作。但它有一些关于声明变量类型

的错误

package lab11_2_590510535;
import java.util.Scanner;

class Queue <TYPE>{
    private int count;
    private int front;
    private int rear;
    private int n;
    private Object [] item;
    private TYPE queueFront;
    static void pl(Object a){System.out.println(a);}
    static void p(Object a){System.out.print(a);}

Queue(int x){
    n = x;
    item = new Object[n];
    front = 0;
    rear = -1;
    count = 0;
}

public boolean isEmpty(){
    for(int i = 0 ; i<item.length ; i++){
        if(item[i] != null){return false;}
    }
    return true;
}

public boolean isFull(){
    if(item[item.length] != null){return true;}
    else{return false;}
}

public void enqueue(TYPE v){
    if(!isFull()){
        if(rear < n-1){
            rear++;
            item[rear] = v;
            count++;
        }
    }else{pl("Queue is Full.");}
}
public TYPE dequeue(){
    if(!isEmpty()){
        queueFront = item[front];
        front++;
        count++;
    }else{p("Queue is empty.");}
    return queueFront;
}
public void show(){
 for(int i = 0 ; i <item.length ; i++){
     if(item[i] !=  null){p(item[i] + ", ");}
 }
}


public class Lab11_2_590510535 {
    static void pl(Object a){System.out.println(a);}
    static void p(Object a){System.out.print(a);}
/**
 * @param args the command line arguments
 */
public static void main(String[] args) {
    // TODO code application logic here
    Scanner keyboard = new Scanner(System.in);
    char choice;
    int N;
    p("Enter N: ");
    N = keyboard.nextInt();
    p("Choice input type; int(1) , char(2): ");
    choice = keyboard.next().charAt(0);
    if(choice == '1'){Queue <Integer> q = new Queue(N);}
    else if(choice == '2'){Queue <Character> q = new Queue(N);}
    do{
        pl("1) enqueue"); pl("2) dequeue"); pl("3) show"); pl("4) exit");
        p("Enter function number : ");
        choice = keyboard.next().charAt(0);
        if(choice == '1'){
            p("Enter data: ");
            Object s = keyboard.next();
            q.enqueue(s);
        }
        else if(choice == '2'){Object s =  q.dequeue();
            pl(s);
        }
        else if(choice == '3'){q.show();}
    }while(choice != '4');

    }
}

1.用户输入选择后，我在do ... while循环中使用类型转换创建通用对象，但找不到“q”。

2.在public TYPE dequeue（）方法行“queueFront = item [front];”对象无法转换为TYPE，我该如何修复它。

Answer 1

尝试将private Object [] item更改为private TYPE [] item。您还需要知道如何为您的示例创建通用数组： How to create a generic array? How to create a generic array in Java?

您需要将item = new Object[n];更改为item = (TYPE[]) new Object[n];

但是你应该避免创建泛型类型，而应该注入它们或使用工厂来创建它们。

对于具有类型转换的泛型类，不能“新对象”

1 个答案: