Develop Reference

How can I add a method that returns a result?

I have been working on these programs.
They don't have any errors but I need to make them return a result in order for them to work properly. More specifically to add a method that returns a result.
The instructions were the following:
Write a program that is split in to methods at least one of which returns a result
This is the first program:
import java.util.Scanner; // Needed to make Scanner available
public class onlineCalculator {
public static void main(String[] args) {
Calculator();
} //END of main method
// Inserting your loan at the start of the year and the amount paid off
// and calculates the amount yet to pay with interest
//
public static void Calculator(){
int a;
int b;
Scanner scanner = new Scanner(System.in);
System.out.print("Amount of loan at start of year? ");
a = scanner.nextInt();
System.out.print("Amount paid off this year? ");
b = scanner.nextInt();
int c;
c= a - b;
double d;
final double e;
d = c * 1.07 * 10.0;
e = (int)d / 10.0;
System.out.println("The new amount owed is (in pounds): " + e);
} //END of Calculator
}
This is the second program:
import java.util.Scanner; // Needed to make Scanner available
public class BodyAge {
public static void main(String[] args) {
CalculateAge();
} // END of main method
// Inserting age and heart rate and stretch distance
//and calculates the body age based on conditions
public static void CalculateAge() {
int age;
int heartRate;
int stretch;
Scanner input = new Scanner(System.in);
System.out.print("What is your age? ");
age = input.nextInt();
System.out.print("What is your heart rate? ");
heartRate = input.nextInt();
if (heartRate <= 62) {
age -= 5; // block of code to be executed if condition1 is true
} else if (62 <= heartRate && heartRate <= 64) {
age--; // block of code to be executed if the condition1 is false and condition2 is
// true
} else if (65 <= heartRate && heartRate <= 70) {
age++; // block of code to be executed if the condition1 and condition2 are false and
// condition3 is true
} else {
age += 2; // block of code to be executed if the condition1 and condition2 and condition3
// are false and condition4 is true
}
System.out.print("How far can you stretch? ");
stretch = input.nextInt();
if (stretch <= 20) {
age += 4; // block of code to be executed if condition1 is true
} else if (20 <= stretch && stretch <= 32) {
age++; // block of code to be executed if the condition1 is false and condition2 is
// true
} else if (33 <= stretch && stretch <= 37) {
age = age + 0; // block of code to be executed if the condition1 and condition2 are false and
// condition3 is true
} else {
age = age + 3; // block of code to be executed if the condition1 and condition2 and condition3
// are false and condition4 is true
}
System.out.println("Your body's age is " + age);
} //END of CalculateAge
}

Here's an example of one possible way you might consider breaking up a class into using some methods with returns. Let's take your first class for this example. You frequently are taking input from your user.
Scanner scanner = new Scanner(System.in);
System.out.print("Amount of loan at start of year? ");
a = scanner.nextInt();
System.out.print("Amount paid off this year? ");
b = scanner.nextInt();
This could potentially be broken out into another method for condensed reusability.
public static int askForInt(Scanner scanner, String message) {
System.out.print(message);
return scanner.nextInt();
}
From there you can replace your calls for information with this method. Full example:
import java.util.Scanner; // Needed to make Scanner available
public class OnlineCalculator {
public static void main(String[] args) {
calculator();
} //END of main method
// Inserting your loan at the start of the year and the amount paid off
// and calculates the amount yet to pay with interest
//
public static void calculator(){
int a;
int b;
Scanner scanner = new Scanner(System.in);
a = askForInt(scanner, "Amount of loan at start of year? ");
b = askForInt(scanner, "Amount paid off this year? ");
scanner.close();
int c;
c= a - b;
double d;
final double e;
d = c * 1.07 * 10.0;
e = (int)d / 10.0;
System.out.println("The new amount owed is (in pounds): " + e);
} //END of Calculator
public static int askForInt(Scanner scanner, String message) {
System.out.print(message);
return scanner.nextInt();
}
}

First program,
You could for example split your calculate() method into 2 method and move your int variable "a" and "b" in the main() method
1ST method:
void getInput(){
...
}
2nd method:
int calculateAndreturnResult(int a, int b) {
...
}
Finally use those method in the main() and print the result :
getInput();
int result = calculateAndreturnResult(){
}
system.out.println(result);

So how Java will work is the compiler will only read commands from the "main" method. So in the case of the calculator, Java will see that you want to run the calculator method, which has a return type of "void" It goes PUBLIC (meaning other classes can see and interact with it) STATIC (basically meaning that the method belongs to the class itself, not instances of the class) VOID ( this is your return type, meaning after the method is done, what is being put back into main) so if you want a method to return something, you need to change the return type. In the case of your calculator project something like this would split it up into 2 methods one of which returns something:
public class OnlineCalculator {
public static void main(String[] args) {
Calculator();
} //END of main method
// Inserting your loan at the start of the year and the amount paid off
// and calculates the amount yet to pay with interest
//
//this will return an int type
public static int loanDifference(int amountOwed, int amountPaid) {
int c = amountOwed - amountPaid;
return c;
}
// this will return a double type
public static double newAmountOwed(double d) {
double e = (int)d / 10.0;
return e;
}
public static void Calculator(){
int a;
int b;
Scanner scanner = new Scanner(System.in);
System.out.print("Amount of loan at start of year? ");
a = scanner.nextInt();
System.out.print("Amount paid off this year? ");
b = scanner.nextInt();
scanner.close();
int c = loanDifference (a, b);
double d;
d = c * 1.07 * 10.0;
final double e = newAmountOwed(d);
System.out.println("The new amount owed is (in pounds): " + e);
} //END of Calculator
}
seems like they want you to put more code in, but the idea is that they want you to know how to use methods that work together to make something at the end!
use the same idea with the other one!

Returning/Passing Variables in Java

I am a beginning programmer and we were assigned to implement methods into a code. I had this grade average code working fine, but once I broke it up into methods, I could not get the return functions to work. I have tried moving brackets and rearranging the code but to no avail. I believe it may have to do with the scope of my variables... Thanks in advance :)
package milsteadgrades;
import java.util.Scanner;
public class MilsteadGrades {
public static void main(String[] args)
{
//Call methods to execute program.
displayInfo();
double numOfgrades = getInput();
double average = getAverage(numOfgrades);
char letgrade = determineLetterGrade(average);
displayGrades(average, letgrade);
}
public static void displayInfo()
{
System.out.println("Mallory Milstead");
System.out.println("This program will prompt the user for a number of
grades"
+ " and each grade. Then the program calculates and displays the average and
letter"+" grade.");
}
public static double getInput()
{
//Prompt user to enter number of grades and assign that number to
numOfgrades.
System.out.print("How many grades would you like to average? ");
Scanner keyboard = new Scanner(System.in);
double numOfgrades = keyboard.nextDouble();
return numOfgrades;
}
public static double getAverage(numOfgrades)
{
//Prompt the user to enter grades.
System.out.println("Enter exam scores : ");
Scanner keyboard = new Scanner(System.in);
double total = 0;
for (double i = 0; i < numOfgrades; i++) {
double grade = keyboard.nextDouble();
total+=grade;}
double average = total/numOfgrades;
return average;
}
public static char determineLetterGrade(average)
{ double testscore = average;
char letgrade;
if (testscore >= 90)
{
letgrade = 'A';
} else if (testscore >= 80)
{
letgrade = 'B';
} else if (testscore >= 70)
{
letgrade = 'C';
} else if (testscore >= 60)
{
letgrade = 'D';
} else
{
letgrade = 'F';
}
return letgrade;
}
public static void displayGrades(average, letgrade)
{
System.out.println("The average of the grades is "+average+ " and the
letter grade"+ " is " + letgrade+".");}
}
Beginning with the line -public static double getAverage(numOfgrades)-, I continuously get "cannot find symbol" error message. None of my variables is being recognized.

You need to declare the type of the argument of getAverage. Like
public static double getAverage(double numOfgrades)
Similiarly for your other methods(not modules). Have a read of this or this for tips.

BMI calculator errors

While doing an assignment for a BMI calculator I keep running into problems with the compiler and the method being used.
The assignment requires me to call a function double bmi to calculate the bmi. I am having problems getting the calling of the function correct. Any help would be great.
One of the errors:
Prog5.java:44: error: illegal start of expression
public static double calculateBmi(double height, double total) {
^
Code:
import java.util.Scanner;
public class Prog5 {
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
double avgweight,bmi,total,wReading;
int heightft,heightin,height,k;
String category,weightreading;
System.out.print("Enter the height(in feet and inches separated by spaces): ");
heightft = sc.nextInt();
heightin = sc.nextInt();
height = ((heightft*12)+heightin);
System.out.print("Enter the weight values separated by spaces followed by a negative number: ");
wReading = sc.nextDouble();
While (wReading >=0);
{
total = wReading+total;
Count++;
wReading = sc.nextDouble();
}
avgweight = 0;
total = 0;
weightreading = "Weight readings: " + wReading;
avgweight = total/Count;
public static double calculateBmi(double height, double total) {
{
double bmi = 0;
double total = 0;
double height = 0;
bmi = (height*703) / (total*total);
}
return bmi;
}
if ( bmi > 30)
category=("Obese");
else if (bmi >= 25)
category=("Overweight");
else if (bmi >= 18.5)
category=("Normal");
else {
category=("Underweight");
}
System.out.println("");
System.out.println("Height: "+ heightft + " feet " + heightin + " inches" );
System.out.println("Weight readings: "+ count);
System.out.println("Average weight: " + avgweight + "lbs");
System.out.println("");
System.out.printf("BMI: " + "%.2f", bmi);
System.out.println("");
System.out.println("Category: " + category);
System.out.println("");
}
private static void ElseIf(boolean b) { }
private static void If(boolean b) { }
}

The problem you mention is due to you beginning another method inside main. You instead want a structure something like:
public class Prog5
{
public static void main(String[] args)
{
// code here
}
public static double calculateBMI(double height, double total)
{
//other code
}
}

Your problem is that you are attempting to define a method (namely, public static double calculateBMi) inside a method (public static void main), and Java does not let you do that. (Basically, methods that aren't main need to be attached to a class.)
In the future, you may want to look around before asking this kind of question, since duplicate versions of this have been asked. Your question is basically: Function within a function in Java

Java programing bank account code [duplicate]

This question already has answers here:
Syntax error on token(s), misplaced construct(s) Code Help Needed
(2 answers)
Closed 9 years ago.
I am using eclipse to look at my code and the most common error that comes up is "Syntax error on token(s), misplaced construct(s)" I'm not sure what I am doing wrong, but I am fairly new to Java.
My code is supposed to withdraw an indicated (user-input) amount from a bank account, I started off with $10,000 and set up the program so that if the withdrawal amount is less than 0 or greater than $10,000 it will trigger an assertion error.
class ThreadsUnitProject2 {
public static void main(Sting args [])
// Field member
private int balance;
public void BankAccount()
{
balance = 10000;
}
public int withdraw(int amount)
{
// Subtract requested amount from balance
balance-=amount;
// Return requested amount
return amount;
}
public int getBalance()
{
return balance;
}
import java.util.Scanner;
class BankAccountTester extends BankAccount
{
public static void main(String[] args)
{
Scanner scan = new Scanner(System.in);
BankAccount myAccount = new BankAccount();
System.out.println("Balance = " + myAccount.getBalance());
System.out.print("Enter amount to be withdrawn: ");
int amount = scan.nextInt();
assert (amount >= 0 && amount <= myAccount.getBalance()):"You can't withdraw that amount!";
myAccount.withdraw(amount);
System.out.println("Balance = " + myAccount.getBalance());
}
Thank you for all of your help!

rename your class "ThreadsUnitProject2" to BankAccount and remove main() method from that and make BankAccountTester class public and finally remove void from BankAccount constructor

After seeing so many issues in your code I decided I should just fix it and let you try to learn from the solution seen below.
This should be the first Class file.
public class BankAccount {
private int balance;
public BankAccount() { //constructor
balance = 10000;
}
public int withdraw(int amount) {
balance -= amount;
return amount;
}
public int getBalance() {
return balance;
}
}
This should be your second Class file. This one will contain your main method which will test your BankAccount class.
import java.util.Scanner;
public class BankAccountTester {
public static void main(String[] args) {
Scanner scan = new Scanner(System.in);
BankAccount myAccount = new BankAccount();
System.out.println("Balance = " + myAccount.getBalance());
System.out.print ("Enter amount to be withdrawn: ");
int amount = scan.nextInt();
assert (amount >= 0 && amount <= myAccount.getBalance()) : "You can't withdraw that amount!";
myAccount.withdraw(amount);
System.out.println("NewBalance = " + myAccount.getBalance());
}
}
Please read and review this link to proper coding conventions.

How to create an equals Method in Java for 2 credit cards

so I'm having an issue writing my code such that i will be able to create an equals method that will return true if 2 credit cards are equal if they have the same Security code, company and account number.
Heres my code so far.
public class CreditCard {
private double balance;
public static double interestRate;
public static String personname;
public static String company;
public static double creditLine;
public CreditCard ()
{
balance = 0;
}
public static void setIntRate (double rate)
{
interestRate = rate;
System.out.println("The Interest rate for this card is : " + interestRate);
}
public static double getIntRate ()
{
return interestRate;
}
public static void setPersonName (CreditCard card ,String pName)
{
personname = pName;
System.out.println("Name on card: " + personname);
}
public static void setCompany (CreditCard card, String compName)
{
company =compName;
System.out.println("The Company name is : "+ company);
}
//creates new card number
public static void CardNum (CreditCard card)
{
int[] accountnumber = new int [16];
Random generator = new Random ();
for (int i =0; i<16; i++)
accountnumber [i] = (int)(Math.random()*10);
System.out.println ("The Account number for this card is: " + (java.util.Arrays.toString(accountnumber))+"");
}
//Creates new securitycode
public static void getSecurityCode (CreditCard card)
{
int[] securitycode = new int [3];
Random generator = new Random ();
for (int i =0; i<3; i++)
securitycode [i] = (int)(Math.random()*10);
System.out.println ("The security code for this card is: " + (java.util.Arrays.toString(securitycode))+"");
}
public static void setexpirationdate(int MM, int YY)
{
System.out.println("The expiration date for this card is: " + MM + "/"+ YY + "\n");
}
public static void setCreditLine (int cLine){
creditLine =cLine;
}
public static void getCreditLine (CreditCard card)
{
System.out.println( " CreditLine is : $" + creditLine);
}
// buys something
public void buyWithCreditCard (double amount)
{
balance = balance + amount;
}
//Inserts money to reduce balance
public double paybalance (double amount)
{
if (balance >= amount){
balance = balance - amount;
roundBalance();}
else{
creditLine = creditLine + (amount - balance);
balance = 0;
System.out.println("Your new CreditLine is: "+creditLine);
roundBalance();
}
return amount;
}
// adds interest to balance
public void addInterest ()
{
double interest = balance * getIntRate ();
balance = balance + interest;
roundBalance ();
}
private void roundBalance ()
{
balance = (double)(Math.round(balance*100))/100;
}
public double checkBalance (){
return balance;
}
//Shows Credit Card Debt
public static void showBalance (CreditCard card)
{
System.out.print(card.balance);
}
}
and then the class that utilizes the CreditCard Class.
public class CreditCardDemo {
public static void main (String [] args)
{
//Creates cards 1 and 2
CreditCard firstCard = new CreditCard ();
CreditCard secondCard = new CreditCard ();
//Calls for card info 1
System.out.println("First card Information is:");
CreditCard.setPersonName(firstCard,"John White");
//CreditCard.getName(firstCard);
CreditCard.setCreditLine(600);
CreditCard.getCreditLine(firstCard);
CreditCard.setCompany(firstCard,"Visa");
CreditCard.setIntRate(0.02);
CreditCard.CardNum(firstCard);
CreditCard.getSecurityCode(firstCard);
CreditCard.setexpirationdate(11, 17);
//call for card info 2
System.out.println("Second card Information is:");
CreditCard.setPersonName(secondCard,"Jack Black");
CreditCard.setCreditLine(2600);
CreditCard.getCreditLine(secondCard);
//CreditCard.getName(secondCard);
CreditCard.setCompany(secondCard,"Discover");
CreditCard.setIntRate(0.02);
CreditCard.CardNum(secondCard);
CreditCard.getSecurityCode(secondCard);
CreditCard.setexpirationdate(10, 19);
//Purchases
System.out.println("\nYou bought something for $5.00");
firstCard.buyWithCreditCard (5.00);
System.out.println("You bought another item for $12.00");
firstCard.buyWithCreditCard(12.00);
System.out.println("You bought another item for $15.00");
firstCard.buyWithCreditCard(15.00);
System.out.println("You bought another item for $33.42");
firstCard.buyWithCreditCard(33.42);
//Display Current Balance
System.out.print("You currently owe: $");
CreditCard.showBalance(firstCard);
//Interest Adds onto it
if (firstCard.checkBalance () > 50.00){
System.out.println("\nInterest has been added");
firstCard.addInterest ();
System.out.print("Your new balance is : $");
CreditCard.showBalance(firstCard);
System.out.println("");
//Payment
System.out.println("You have overpaid your balance.");
firstCard.paybalance (70);
System.out.print("Your new balance is : $");
CreditCard.showBalance(firstCard);
}
}
}
So if anyone could show me how to create a method in the CreditCard class that would allow me to check if the firstCard and secondCard, that would be great. Thanks a bunch :)

If you use NetBeans, you can simply auto-generate the equals function (not sure about Eclipse). Other than that it boils down to overwriting the equals function of Object.
Make sure to check that both are of the same class and make sure to check for null. Java recommends to as well overwrite the hashCode function, however that depends on your use-case.

first of all, i'm not that advanced in java, but this seems simple enough still.
The problem here seems that the security code is never saved (the method getSecurityCode is void and all variables are only local)
Same goes for the company
nonetheless, here's an example, assuming you fixed that and made a method getCode that returns the code (as int) and a method getAccountNumber, that returns that number (as int). (and assuming it's no problem to make those methods public)
public boolean equals(CreditCard creditCard1, CreditCard creditCard2){
if (creditCard1 == null || creditCard2 == null)
return creditCard1 == creditCard2;
boolean equalCode = (creditCard1.getCode() == creditCard2.getCode());
boolean equalCompany = creditCard1.company.equals(creditCard2.company);
boolean equalAccountNumber = (creditCard1.getAccountNumber() == creditCard2.getAccountNumber());
return equalCode && equalCompany && equalAccountNumber;
}
It would be good practice to make the variables private and make some getters, but that's up to you.