数组Java初学者
我无法将值存储到我的数组Java初学者,java,arrays,Java,Arrays,我无法将值存储到我的monthlySales数组中。另外,如何检索要在其他方法(如totalSales)中使用的值?另外,我在getSales()方法中有错误 import java.util.Scanner; import java.text.DecimalFormat; public class SalesTracking { static DecimalFormat f = new DecimalFormat ("$#,##0.00"); static Scanner
monthlySales
数组中。另外,如何检索要在其他方法(如totalSales
)中使用的值?另外,我在getSales()
方法中有错误
import java.util.Scanner;
import java.text.DecimalFormat;
public class SalesTracking
{
static DecimalFormat f = new DecimalFormat ("$#,##0.00");
static Scanner input = new Scanner (System.in); //create a scanner object that reads from the keyboard (System.in)
private static final double[] monthlySales = new double[12]; //create monthlysales array
private static final String[] monthArray = {"January" , "February" , "March" , "April", "May",
"June", "July", "August", "September", "October",
"November", "December"}; //create 12-month array
static void getSales(){
int size = monthArray.length;
for (int i = 0; i < size; i++){
System.out.print("Please Enter Sales for " + monthArray[i] + ":");
monthlySales[i] = input.nextDouble();
} //get sales method to store values into monthlysales
}
public static void main(String[] args){
getSales();
totalSales();
computeHighestMonth(monthlySales);
computeLowestMonth(monthlySales);
import java.util.Scanner;
导入java.text.DecimalFormat;
公共类销售跟踪
{
静态DecimalFormat f=新的DecimalFormat($#,##0.00”);
静态扫描仪输入=新扫描仪(System.in);//创建从键盘(System.in)读取的扫描仪对象
private static final double[]monthlySales=new double[12];//创建monthlySales数组
私有静态最终字符串[]monthArray={“一月”、“二月”、“三月”、“四月”、“五月”,
“六月”、“七月”、“八月”、“九月”、“十月”,
“十一月”、“十二月”};//创建12个月数组
静态void getSales(){
int size=monthArray.length;
对于(int i=0;i
正如评论中所说,将此方法移到main之外。
然后,您需要在main中创建此类的实例,并通过构造函数或作为参数传递input
这是您的代码的修改版本(我没有测试过,但应该可以工作)
import java.util.Scanner;
公共类销售跟踪
{
私人静态最终双月销售[]=新双月[12];
私有静态最终字符串[]monthArray={“一月”、“二月”、“三月”、“四月”、“五月”,
“六月”、“七月”、“八月”、“九月”、“十月”,
“11月”、“12月”};
静态无效totalSales(){
}
静态无效平均销售额(){
}
静态空隙最高月份(){
}
静态无效下限月(){
}
公共静态void getSalesUsingStaticMethodWhichBelongsToClass(双输入)
{
SalesTracking SalesTracking=新建SalesTracking();
salesTracking.GetSalesUsingNonStaticMethod,该方法属于实例和建议(输入);
}
public void GetSalesUsingNonStaticMethod,该方法属于实例和建议(双输入)
{
int size=monthArray.length;
对于(int i=0;i
像这样的长方法名称在主类中不需要,但在单元测试中是可以使用的,建议使用。我刚刚用它们来说明问题的要点 无法将值存储到monthlySales数组中 首先,避免使用C语法,并将声明编写为:
private static final double[]monthlySales=new double[12];
这强调了monthlySales
属于double[]
类型。现在,请回答您的问题。下面一行是给您带来麻烦的原因
monthlySales=input.nextDouble();
当您将monthlySales
声明为final
时,实际上意味着您不能让引用变量指向任何其他对象。在这里,您试图使变量指向一个双精度
,这两种情况都不能发生,因为变量必须指向一个双精度[]
和最终声明
相反,您希望这样做,因为更改数组中的值非常好(Java的final
关键字有点奇怪):
monthlySales[i]=input.nextDouble();
另外,我在publicstaticvoidgetsales()方法上有错误
这是因为您已经在main()
中定义了getSales
方法。在Java中,您不能在其他方法中定义方法(但是可以通过类来定义)
我相信您希望完全去掉getSales
定义,因为您的主客户端似乎是从标准输入读取的。如果您需要从另一个类访问数组,请在main
之外定义getter方法
另外,如何检索要在其他方法(如totalSales)中使用的值
由于您已将值分配给静态成员monthlySales
和monthArray
,因此您已经可以从其他静态方法访问这些变量
请注意,由于没有非静态变量或方法,因此无法有意义地创建多个SalesTracking
实例,因为所有实例将共享同一组数据
void(无效类型)和getSales(参数getSales的修饰符非法;只允许final)上的错误
这些源于getSales
在main
中的定义。如果您在外部定义该方法或将其完全删除,就可以了
编辑:修复您的getSales()
如下:
public static void getSales() {
try (
Scanner input = new Scanner(System.in); // try-with-resources
) {
int size = monthArray.length;
for (int i = 0; i < size; i++){
System.out.print("Please Enter Sales for " + monthArray[i] + ":");
monthlySales[i] = input.nextDouble();
}
} catch (IOException e) {
System.out.println(e.getMessage());
}
}
public static void main(String[] args) {
getSales();
}
publicstaticvoidgetsales(){
试一试(
Scanner input=new Scanner(System.in);//尝试使用资源
) {
int size=monthArray.length;
用于(int i)
public static void getSales() {
try (
Scanner input = new Scanner(System.in); // try-with-resources
) {
int size = monthArray.length;
for (int i = 0; i < size; i++){
System.out.print("Please Enter Sales for " + monthArray[i] + ":");
monthlySales[i] = input.nextDouble();
}
} catch (IOException e) {
System.out.println(e.getMessage());
}
}
public static void main(String[] args) {
getSales();
}
class Sales {
public Month getMonth() {
return month;
}
public void setMonth(Month month) {
this.month = month;
}
private Month month;
public double getSales() {
return sales;
}
public void setSales(double sales) {
this.sales = sales;
}
private double sales;
@Override
public String toString() {
return "month->" + getMonth() + ",sales->" + getSales();
}}
/**
* @author puruidong
* @version 2015-07-10
*/
public class Main {
private static final double monthlySales[] = new double[12];
private static final String[] monthArray = {"January", "February", "March", "April", "May",
"June", "July", "August", "September", "October",
"November", "December"};
private Set<Sales> salesList = new HashSet<Sales>(12);
public void totalSales() {
double count = salesList.stream().mapToDouble(new ToDoubleFunction<Sales>() {
@Override
public double applyAsDouble(Sales value) {
return value.getSales();
}
}).sum();
System.out.println("total->" + count);
}
static void averageSales() {
}
static void highestMonth() {
}
static void lowestMonth() {
}
public void showSales() {
salesList.forEach((x) -> {
System.out.println(x.toString());
});
}
public void getSalesUsingNonStaticMethodWhichBelongsToInstanceAndRecommended(Scanner sc) {
int i = 0;
while (i <= 11) {
System.out.println("Please enter a month to be recorded?(1-12)");
int months = sc.nextInt();
Sales sales = new Sales();
switch (Month.of(months)) {
case JANUARY:
sales.setMonth(Month.JANUARY);
break;
case FEBRUARY:
sales.setMonth(Month.FEBRUARY);
break;
case MARCH:
sales.setMonth(Month.MARCH);
break;
case APRIL:
sales.setMonth(Month.APRIL);
break;
case MAY:
sales.setMonth(Month.MAY);
break;
case JUNE:
sales.setMonth(Month.JUNE);
break;
case JULY:
sales.setMonth(Month.JUNE);
break;
case AUGUST:
sales.setMonth(Month.AUGUST);
break;
case SEPTEMBER:
sales.setMonth(Month.SEPTEMBER);
break;
case OCTOBER:
sales.setMonth(Month.OCTOBER);
break;
case NOVEMBER:
sales.setMonth(Month.NOVEMBER);
break;
case DECEMBER:
sales.setMonth(Month.DECEMBER);
break;
default:
System.err.println("--input error--");
break;
}
if (sales.getMonth() != null) {
sc.reset();
System.out.println("Please enter turnover:");
double turnover = sc.nextDouble();
sales.setSales(turnover);
salesList.add(sales);
}
i++;
}
showSales();
System.out.println("----------------------------");
totalSales();
}
public static void main(String[] args) {
Scanner input = new Scanner(System.in);
Main salesTracking = new Main();
salesTracking.getSalesUsingNonStaticMethodWhichBelongsToInstanceAndRecommended(input);
}//end main
}//end class
Please enter a month to be recorded?(1-12)
1
Please enter turnover:
1
Please enter a month to be recorded?(1-12)
2
Please enter turnover:
2
Please enter a month to be recorded?(1-12)
3
Please enter turnover:
3
Please enter a month to be recorded?(1-12)
4
Please enter turnover:
4
Please enter a month to be recorded?(1-12)
5
Please enter turnover:
5
Please enter a month to be recorded?(1-12)
6
Please enter turnover:
6
Please enter a month to be recorded?(1-12)
7
Please enter turnover:
7
Please enter a month to be recorded?(1-12)
8
Please enter turnover:
8
Please enter a month to be recorded?(1-12)
9
Please enter turnover:
9
Please enter a month to be recorded?(1-12)
10
Please enter turnover:
10
Please enter a month to be recorded?(1-12)
11
Please enter turnover:
11
Please enter a month to be recorded?(1-12)
12
Please enter turnover:
12
------------------------------
month->DECEMBER,sales->12.0
month->JANUARY,sales->1.0
month->APRIL,sales->4.0
month->AUGUST,sales->8.0
month->MAY,sales->5.0
month->MARCH,sales->3.0
month->JUNE,sales->7.0
month->OCTOBER,sales->10.0
month->NOVEMBER,sales->11.0
month->FEBRUARY,sales->2.0
month->JUNE,sales->6.0
month->SEPTEMBER,sales->9.0
----------------------------
total->78.0