Question

我需要从数组中获取一个数字并将其初始化为变量，以便将其用作对象。我不确定它是否只是，

例如

int smallSpaces = 1;。

有谁知道我怎么能这样做？

public class Port {
    public static void main(String[] args) throws IOException {
        Scanner console = new Scanner(System.in);

        String shipSize = null;
        String shipName = null;

        int smallSpaces = 1;
        int mediumSpaces = 2;
        int largeSpaces = 3;

        int[][] dockSpaces = {
            {1, 1, 1, 1, 1, 2, 2, 2, 3, 3},
            {1, 1, 1, 1, 1, 2, 2, 2, 3, 3},
            {1, 1, 1, 1, 1, 2, 2, 2, 3, 3},
        };

        int waitingList = 10;
        int menuChoice = 0;

        while (true) {
            System.out.println("SHIP PORT APPLICATION");
            System.out.println("\n1. Add ship to port.");
            System.out.println("\n2. Remove ship from port.");
            System.out.println("\n3. View report.");
            System.out.println("\n4. Exit.");

            menuChoice = console.nextInt();

            switch (menuChoice) { // Using a switch case for the menu options
                case 1:
                    System.out.println("Add ship to port");
                    break;
                case 2:
                    System.out.println("Remove ship from port");
                    break;
                case 3:
                    System.out.println("View report");
                    break;
                case 4:
                    System.out.println("Exit");
                    break;
                default:
                    System.out.println("Invalid Choice");
            }

            try {
                FileWriter write = new FileWriter("PortLog.txt", true);
                BufferedWriter out = new BufferedWriter(write);

                if (menuChoice == 1) {
                    System.out.println("Please select ship size(1. Cargo /n 2.Container /n 3. SuperContainer)");
                    shipSize = console.next();

                    System.out.println("Please enter the name of your ship");
                    shipName = console.next();

                    if (shipSize.equals("1")) {
                        smallSpaces++;
                        System.out.println("test");
                        write.write("SMALL"); // Printing line to output file about the transaction details
                        out.newLine();  //Adding new line to file writer
                        out.close();
                    }
                }
            } catch (Exception e) {
                System.out.println("Error: " + e.getMessage());
            }
        }
    }
}

Answer 1

初始化int

int a = 1;

就够了。但是，虽然这是一个变量，但它不是一个对象，它是一种原始类型。对象需要使用关键字new创建，而原始类型不需要，java原始类型是byte，short，int，long，float，double，boolean，char。从初始化角度来看，字符串是一种特殊情况，因为它可以用字符串文字初始化。

基元：

int a = 1;
char c = 'c';
boolean b = true;
...

物件：

Object a = new Object();
ClassA class = new ClassA();
...

Answer 2

如果你想使用一个对象，Java中的原始类型也有相应的对象，如Integer，Double等。例如：

Integer myInt = new Integer(5);

Answer 3

我需要从数组中获取一个数字并将其初始化为变量，以便将其用作对象。我不确定它是否只是

int[] nums = {1,2,3,4,5};
int myVar = nums[0];   //will get first array element (initialize it to a variable)

如果您想将用于对象。

int[] nums = {1,2,3,4,5};
MyClass m = new MyClass(nums[0]);   //m's value (x) will be updated to num[0]

class MyClass
{
    int x;
    public MyClass(int x){  //Constructor
        this.x = x;
    }
}

如果您想将用作对象。

//Use a wrapper class according to the array element's data type:
Integer val = new Integer(nums[0]);

如何从数组初始化数字

3 个答案: