我收到一个错误，作为非静态变量，无法从静态上下文帐户account1=新帐户（112220000，.045）引用该错误；

Question

我已经一遍又一遍地写了这个程序，有人能告诉我我缺少了什么吗，看起来这是一个我没有抓住的小错误。

以下是我正在努力实现的目标：

设计一个名为帐户的类，其中包含：

• 帐户名为id的私有int数据字段（默认值为0）

编写一个测试程序，创建一个帐户对象，帐户ID为1122，余额为20,000美元，年利率为4.5%。使用提取方法提取2,500美元，使用存款方法存入3,000美元并打印余额、每月利息以及创建此帐户的日期。

错误是非静态变量，无法从静态上下文中引用

账户账户1=新账户（1122, 20000, .045)；

import java.util.Date;
class assignExam {

public static void main(String[] args) {

Account account1 =  new Account(1122, 20000, .045);
account1.withdraw(2500);
account1.deposit(3000);
java.util.Date dateCreated = new java.util.Date();
System.out.println("Date Created:" + dateCreated);
System.out.println("Account ID:" + account1.id);
System.out.println("Balance:" + account1.getBalance());
System.out.println("Interest Rate:" + account1.getAnnualInterestRate());
System.out.println("Balance after withdraw of 2500:" +       account1.getAnnualInterestRate());
System.out.println("Balance after deposit of 3000:" + account1.getAnnualInterestRate());
System.out.println("Monthly Interest:" + account1.id);

System.out.println("Process completed.");
}

class Account {
//define variables
private int id;
private double balance; // balance for account
private double annualInterestRate; //stores the current interest rate
private Date dateCreated; //stores the date account created

//no arg construtor
Account () {
    id = 0;
    balance = 0.0;
    annualInterestRate = 0.0;
}
//constructor with specific id and initial balance
Account(int newId, double newBalance) {
    id = newId;
    balance = newBalance;
}
Account(int newId, double newBalance, double newAnnualInterestRate) {
    id = newId;
    balance = newBalance;
    annualInterestRate = newAnnualInterestRate;
}
//accessor/mutator methods for id, balance, and annualInterestRate
public int getId() {
    return id;
}
public double getBalance() {
    return balance;
}
public double getAnnualInterestRate() {
    return annualInterestRate;
}
public void setId(int newId) {
    id = newId;
}
public void setBalance(double newBalance) {
    balance = newBalance;
}
public void setAnnualInterestRate(double newAnnualInterestRate) {
    annualInterestRate = newAnnualInterestRate;
}
//accessor method for dateCreated
public void setDateCreated(Date newDateCreated) {
    dateCreated = newDateCreated;
}
//define method getMonthlyInterestRate
double getMonthlyInterestRate() {
    return annualInterestRate/12;
}
//define method withdraw
double withdraw(double amount) {
    return balance -= amount;
}   
//define method deposit
double deposit(double amount) {
    return balance += amount;   
}
}

}

Answer 1

类帐户应为静态

Answer 2

罗伯托的回答是正确的，但有一点背景。

您当前已将帐户声明为assignExam类中的嵌套类。它不是声明为静态的，这意味着要创建该类的实例，还需要创建assignExam的实例。

因此，您可以使用以下命令使类成为静态的：

static class Account {

或者您可以将帐户类移出您的askExam类，这将自动使其成为一个独立的类，因此是静态的，因为它不再嵌套在另一个类中。