Question

我遇到的问题如下：我创建了两个代表船只停靠空间的数组。第一个数组ship对象（shipName和size - 通常是Super-Container）可以保存在数组中，如果没有空格，那么它将被添加到一个等待列表数组中。

我只能在等候名单上添加一艘船，并说它已满。你能帮我吗？这是我的dock类，waitingList（）中的问题：

import java.util.*;

public class Main {

static Scanner scan = new Scanner(System.in);
private static Ship[] dock1 = new Ship[10];
private static Ship[] waitingList = new Ship[10];

public static void main(String[] args) {
    menu();
}

public static void menu() {


    Scanner scan = new Scanner(System.in);


    while (true) {

        System.out.println("Choose an option: 1-3");
        System.out.println("1. Dock");
        System.out.println("2. Undock");
        System.out.println("3. Status");

        int menu = scan.nextInt();
        switch (menu) {
            case 1:
                System.out.println("1. Dock");
                dock();
                break;
            case 2:
                System.out.println("2. Undock");
                undock();
                break;
            case 3:
                System.out.println("3. Status");
                printDock();
                printWaitingList();
                break;
            case 4:
                System.out.println("4. Exit");
                System.exit(0);
            default:
                System.out.println("No such option");
                break;
        }
    }
}


public static void dock() {

    System.out.println("Enter ship's name: ");
    String name = scan.nextLine();

    System.out.println("Enter ship's size: ");
    String size = scan.nextLine();

    System.out.println("Enter the ships dock:");
    //Check if the dock number is valid
    int i = Integer.valueOf(scan.nextLine());
    if (i >= 0 && i < 10 && dock1[i] == null) {
        int c = 0;
        int co = 0;
        int sco = 0;
        for (int j = 0; j < dock1.length; j++) {
            if (dock1[j] != null &&         dock1[j].getShipSize().equals("Cargo")) {
                c++;
            }
            if (dock1[j] != null && dock1[j].getShipSize().equals("Container")) {
                co++;
            }
            if (dock1[j] != null && dock1[j].getShipSize().equals("Super-Container")) {
                sco++;
            }
        }

        if (c < 10 && co < 5 && sco < 2) {
            //Add ship to the dock
            dock1[i] = new Ship(name, size);
            System.out.println("Enough space you can dock");
            System.out.println("Ship has been docked");
        } else {
            System.out.println("You cannot dock");
            waitingList(name,size);
        }

    } else {
        System.out.println("Couldn't dock");
        waitingList(name, size);
    }

}


public static void undock() {
    System.out.println("Status of ships: ");
    printDock();
    System.out.println("Enter ship's name to undock: ");
    String name = scan.nextLine();
    //System.out.println("Enter ship's size to undock: ");
   // String size = scan.nextLine();

    for (int i = 0; i < dock1.length; i++) {
        if (dock1[i] != null && dock1[i].getShipName().equals(name)) {
            dock1[i] = null;
            System.out.println("Ship removed");
            /// HERE CHECK IF SHIP IN DOCK
            for (int j = 0; j < waitingList.length; j++) {
                if (dock1[i] == null) {
                    // Add ship to the dock
                    dock1[i] = new Ship(waitingList[j].getShipName(), waitingList[j].getShipSize());
                    System.out.println("Move ship from waiting list to dock 1");
                    waitingList[j] = null;
                   break;
                } else {
                    System.out.println("No space in dock1");
                    return;
                }
            }
        } else {
            System.out.println("Ship not docked here");
            break;
        }

    }

}

public static void waitingList(String name, String size){
    System.out.println("Dock 1 is full, ship will try to be added to Waiting List");
    for (int i = 0; i < waitingList.length; i++) {
        if (waitingList[i] == null) { //CHANGE TO ALLOW MORE THAN ONE SHIP
            //Add ship to the dock
            waitingList[i] = new Ship(name, size);
            System.out.println("Enough space added to waiting list");
            break;
        } else {
            System.out.println("No space on waiting list, ship turned away");
            return;
        }
    }

}


public static void printDock() {

    System.out.println("Docks:");

    for (int i = 0; i < dock1.length; i++) {
        if (dock1[i] == null) {
            System.out.println("Dock " + i + " is empty");
        } else {
            System.out.println("Dock " + i + ": " + dock1[i].getShipName() + " " + dock1[i].getShipSize());
        }
    }
}

private static void printWaitingList() {

    System.out.println("Waiting List:");

    for (int i = 0; i < waitingList.length; i++) {
        if (waitingList[i] == null) {
            System.out.println("Dock " + i + " is empty");
        } else {
            System.out.println("Dock " + i + ": " + waitingList[i].getShipName() + " " + waitingList[i].getShipSize());
        }
    }
}
}

Answer 1

试试这个：

public static void waitingList(String name, String size){
    System.out.println("Dock 1 is full, ship will try to be added to Waiting List");
     for (int i = 0; i < waitingList.length; i++) {
         if (waitingList[i] == null) {
                //Add ship to the dock
                waitingList[i] = new Ship(name, size);
                System.out.println("Enough space. Added to waiting list.");
                return;
         } else {
                System.out.println("No space on waiting list at number "+ i +", checking next space."); //Optional
         }
     }
     // Only when no spaces available
     System.out.println("No space on waiting list, ship turned away.");
}

如果你将一艘船添加到waitingList数组，它将永远不会再为null，因此检查（if waitingList[0] == null）将导致执行else部分，其中它是{{1因此循环不会继续，也绝不会尝试检查return。

因此，解决方案是在将船舶添加到列表时退出方法，而不是在我们看到第一个使用的空间时。因此，更改if waitingList[1] == null会有所帮助。

程序无法保存到下一个可用空间

1 个答案: