[英]Can't “new object” for generic class with type casting
該代碼用於學習通用類和堆棧操作。 但是關於聲明變量類型有一些錯誤
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.選擇用戶輸入后,我在do ... while循環中使用類型轉換創建泛型對象,找不到“ q”。
2.在公共TYPE dequeue()方法行中,“ queueFront = item [front];” 無法將對象轉換為TYPE,我該如何解決。
嘗試將private Object [] item
更改為private TYPE [] item
。 另外,您將需要知道如何為示例創建通用數組 : 如何創建通用數組? 如何在Java中創建通用數組?
您將需要更改item = new Object[n];
到item = (TYPE[]) new Object[n];
但是,應避免創建泛型類型,而應注入它們或使用工廠來創建它們。
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