我收到这些错误
Java A5-1\SavingsAccountPart1Test.java:74: error: incompatible types: SavingsAccount cannot be converted to double
if ( savings1.compareTo(savings2) > 0 )
Java A5-1\SavingsAccountPart1Test.java:76: error: incompatible types: SavingsAccount cannot be converted to double
else if (savings1.compareTo(savings2) == 0 )
这是班级
import java.text.DecimalFormat;
public class SavingsAccount
{
private double annualInterestRate; //A double for the yearly interest rate
private double balance; //A double for balance
/**
SavingsAccount A constructor for the annual interest rate and balance
*/
public SavingsAccount()
{
//The balance and interest rate are given default values
annualInterestRate = .005;
balance = 0.00;
}
/**
SavingsAccount A constructor for the annual interest rate and balance
@param rate The annual interest rate
@param bal The balance
*/
public SavingsAccount( double rate, double bal )
{
//Allowing the client to set the balance and interest rate while checking if the values are valid
if (rate < 0)
{
System.out.println("WARNING: Starting balance must not be negative; setting it to $0.00.");
rate = .005;
}
else
annualInterestRate = rate;
if (balance < 0)
{
System.out.println("WARNING: Interest rate must not be negative; setting it to 0.5%.");
bal = 0;
}
else
balance = bal;
}
/**
getInterestRate A method that returns the interest rate
@return The annual interest rate
*/
public double getInterestRate()
{
return annualInterestRate;
}
/**
getBalance A menthod that returns the balance
@return The balance
*/
public double getBalance()
{
return balance;
}
/**
update A method that updates the balance
@param bal The Balance
*/
public void update( double bal )
{
//make a money format, update balance by setting balance to passed in bal and
//check if balance is overdrawn or not
DecimalFormat money = new DecimalFormat("$#,##0.00");
balance += bal;
if (balance < 0)
System.out.println("WARNING: ACCOUNT OVERDRAWN \n Current balance: " + money.format(balance));
}
/**
addInterest A method that will add interest to balance
*/
public void addInterest()
{
//declare a monthly interest and a sub balance, then add interest if balance is greater than 0
double monthlyInterest;
double subBalance;
if (balance > 0)
{
monthlyInterest = annualInterestRate / 12;
subBalance = balance * monthlyInterest;
balance += subBalance;
}
}
/**
compareTo A method to see if balance is bigger or smaller than savings
@param savings The savings
@return The result
*/
public int compareTo( double savings )
{
int result;
if (balance > savings)
result = 1;
else if (balance == savings)
result = 0;
else
result = -1;
return result;
}
/**
toString A method that returns the balance and rate as a string
@return The string of balance and rate
*/
public String toString()
{
//makes format for money and interest rate
//makes a string to hold the balance and rate then returns the string
DecimalFormat money = new DecimalFormat("$#,##0.00");
DecimalFormat rate = new DecimalFormat("0.0%");
String balRate = ("Balance: " + money.format(balance) + "\n" +
"Annual Interest Rate: " + rate.format(annualInterestRate * 100));
return balRate;
}
}
测试类的代码（不允许改变它）
import java.io.*;
import java.util.Scanner;
import java.text.DecimalFormat;
public class SavingsAccountPart1Test
{
public static void main(String args[]) throws IOException
{
double interestRate; // Annual interest rate
double balance; // Balance in the account
double interestEarned; // Interest earned
double amount; // Amount of a deposit or withdrawal
double totalUpdates; // Total amount deposited and withdrawn
// Create a DecimalFormat object for formatting output.
DecimalFormat df = new DecimalFormat("$#,##0.00");
// Display your name
System.out.println("[client] YOUR NAME");
// Welcome message
System.out.println("\n[client] Welcome to the Fleesum Bank"
+ "\n[client] This is the monthly interest calculator");
// Create a Scanner object for keyboard input.
Scanner keyboard = new Scanner(System.in);
// Create a SavingsAccount object using the no-argument constructor
SavingsAccount savings1 = new SavingsAccount();
// Display the initial state of savings1
System.out.println("\n[client] First SavingsAccount object");
System.out.println("\n[client] Balance: " + savings1.getBalance());
System.out.println("[client] Interest Rate: " + savings1.getInterestRate());
System.out.println("\n[client] Using toString:\n" + savings1.toString());
// Create a SavingsAccount object using the 2-argument constructor
SavingsAccount savings2 =
new SavingsAccount(1000, 0.10);
// Display the initial state of savings2
System.out.println("\n[client] Second SavingsAccount object");
System.out.println("\n[client] Balance: " + savings2.getBalance());
System.out.println("[client] Interest Rate: " + savings2.getInterestRate());
System.out.println("\n[client] Using toString:\n" + savings2.toString());
// Test method addInterest when balance is >= 0
savings2.addInterest();
System.out.println("\n[client] Interest computed. New balance: "
+ savings2.getBalance());
// update the balance:
savings2.update( 50 );
System.out.println("\n[client] Fifty dollars deposited. New balance: "
+ savings2.getBalance());
// update, overdrawing the account
savings2.update( -2000 );
System.out.println("\n[client] Two thousand dollars withdrawn. New balance: "
+ savings2.getBalance());
// Test method addInterest when balance is < 0
savings2.addInterest();
System.out.println("\n[client] Interest computed. New balance: "
+ savings2.getBalance());
// Show final state of savings2:
System.out.println("\n[client] Using toString:\n" + savings2.toString()
+ "\n");
// Test compareTo method
if ( savings1.compareTo(savings2) > 0 )
System.out.println("[client] Savings1 has the larger balance");
else if (savings1.compareTo(savings2) == 0 )
System.out.println("[client] Savings1 and Savings2 "
+ "have the same balance");
else
System.out.println("[client] Savings2 has the larger balance");
System.out.println();
}
}
答案 0 :(得分：4)
public int compareTo( double savings )
是您的问题，请将double替换为SavingsAccount并相应地修改方法。
答案 1 :(得分：1)
请注意，该测试会比较SavingsAccount类型的两个对象：
savings1.compareTo(savings2)
虽然您的实施方案将SavingsAccount与double进行了比较：
public int compareTo( double savings )
理想情况下，您应该SavingsAccount实现Comparable（see docs）界面，如下所示：
public class SavingsAccount implements Comparable<SavingsAccount> { ... }
如果没有实施适当的compareTo(SavingsAccount a)，它会抱怨。它应该是这样的：
@Override
public int compareTo(SavingsAccount that) { ... }