Question

我是Java新手，这就要让我把头发撕掉了。请注意我添加了一个打印声明，以确保扫描仪工作正常。

package dknowlton_program5;

import java.util.Scanner;

//Driver ~ Gathers Input

public class DKnowlton_MartianMaker {

static Scanner userInput = new Scanner(System.in);

public static String name;
public static int eyes, arms;

public static void main(String[] String)
{

    printWelcome();
    getName();
    getEyes();
    getArms();

    System.out.print("Your martian " + name + " has... ");

}

public static void printWelcome()
{

    System.out.print("Welcome to the Martian Program Revamped!");

}

public static String getName()
{

    System.out.print("\nWhat would you like to name your martian? ");
    String name = userInput.nextLine();

    System.out.println(name);

    return name;

}

public static int getEyes()
{

    System.out.print("How many eyes does your martian have? ");
    int eyes = userInput.nextInt();

    return eyes;

}

public static int getArms()
{

    System.out.print("How many arms does your martian have? ");
    int arms = userInput.nextInt();

    return arms;

}

}

Answer 1

以下内容应该有效。请注意，顶部的静态变量已被删除，现在我们保存从函数返回的结果。我建议读一下java中的范围，一般来说最好有尽可能低的范围，避免全局变量。

Answer 2

而不是3 你不应该使用x array([['wisD', 'netl', 'stu', '', 'entl'], ['maat', 'wisD', 'stu', '', ''], ['lo', 'nat', 'stu', 'schk', 'maat'], ['nat', 'fatl', 'stu', 'wisB', 'netl'], ['fatl', 'wisB', 'stu', 'wisB', 'ges'], ['schk', 'entl', 'stu', 'ges', ''], ['wisB', '', 'stu', 'nat', 'AK'], ['AK', '', '', '', 'AK'], ['', '', '', '', '']], dtype='<U4')

希望它有效。

编辑：为什么要两次声明String名称？

第二次编辑：试试这个

 np.savetxt("test.csv", x, delimiter=",")
Traceback (most recent call last):
  File "C:\Users\Michiel\AppData\Local\Programs\Python\Python35\lib\site-packages\numpy\lib\npyio.py", line 1158, in savetxt
fh.write(asbytes(format % tuple(row) + newline))
TypeError: a float is required

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "<pyshell#19>", line 1, in <module>
    np.savetxt("test.csv", x, delimiter=",")
  File "C:\Users\Username\AppData\Local\Programs\Python\Python35\lib\site-packages\numpy\lib\npyio.py", line 1162, in savetxt
% (str(X.dtype), format))
TypeError: Mismatch between array dtype ('<U4') and format specifier ('%.18e,%.18e,%.18e,%.18e,%.18e')

}

Answer 3

这个“名字”：

public static String name;

与此“名称”不同：

String name = userInput.nextLine();

您将值分配给第二个，并打印第一个，这就是您获得null的原因。

您只需删除字符串并使用您在开头（第一个）定义的相同“名称”：

package dknowlton_program5;
import java.util.Scanner;

//Driver ~ Gathers Input

public class DKnowlton_MartianMaker {

static Scanner userInput = new Scanner(System.in);

public static String name;
public static int eyes, arms;

public static void main(String[] String)
{

    printWelcome();
    getName();
    getEyes();
    getArms();

    System.out.print("Your martian " + name + " has... ");

}

public static void printWelcome()
{

    System.out.print("Welcome to the Martian Program Revamped!");

}

public static String getName()
{

    System.out.print("\nWhat would you like to name your martian? ");
    name = userInput.nextLine();

    System.out.println(name);

    return name;

}

public static int getEyes()
{

    System.out.print("How many eyes does your martian have? ");
    int eyes = userInput.nextInt();

    return eyes;

}

public static int getArms()
{

    System.out.print("How many arms does your martian have? ");
    int arms = userInput.nextInt();

    return arms;

}

}

为什么我的用户输入在main方法中返回null？

3 个答案: