Java double MAX VALUE

Question

For my assignment I have to create a Gas Meter System for a Gas company to allow employees to create new costumer accounts and amend data such as name and unit costs along with taking depositing  money from their account   I have created my constructor and even added in a method of overloading although I m currently running into a problem when initiating one of my methods I named deposit  this is supposed to take money from the users account while other methods such as recordUnits allows the employee to import a gas meter reading of how many units the customer has used and updates the balance of that customers account which is essentially what the customer owes the company    When testing the program with just preset information when trying to initiate the deposit method I get this   Account deposit Double MAX VALUE     I am not too sure what this means and cannot seem to find anyway of getting past it    test data and code seen below    public class TestGasAccount         public static void main  String    args                GasAccount Account   new GasAccount  223  Havana   TQ  1000            Account getAccNo            Account getName            Account getAddress            Account getUnits            Account getBalance            Account recordUnits 1000           Account getUnits            Account getBalance            Account deposit Double MAX VALUE             break  public class GasAccount        private int intAccNo      private String strName      private String strAddress       private double dblBalance      private double dblUnits      protected double dblUnitCost   0 02         public GasAccount int intNewAccNo String strNewName String strNewAddress double dblNewUnits                  intAccNo   intNewAccNo           strName   strNewName           strAddress   strNewAddress           dblUnits   dblNewUnits           dblBalance   dblNewUnits   dblUnitCost               public GasAccount  int intNewAccNo  String strNewName  String strNewAddress                  intAccNo   intNewAccNo           strName   strNewName           strAddress   strNewAddress               public double deposit  Double dblDepositAmount                 dblBalance   dblBalance - dblDepositAmount           return dblBalance               public String recordUnits  double dblUnitsUsed                  double dblTempBalance            dblTempBalance   dblUnitsUsed   dblUnitCost           dblBalance   dblBalance   dblTempBalance           dblUnits   dblUnits   dblUnitsUsed            return  Transaction Successful                 public int getAccNo                    System out println intAccNo            return intAccNo               public String getName                   System out println strName            return strName                 public String getAddress                   System out println strAddress            return strName                public double getBalance                   System out println      dblBalance            return dblBalance                public double getUnitCost                    return dblUnitCost               public double getUnits                    System out println dblUnits            return dblUnits               public void updateUnitCost  double dblNewUnitCost                  dblUnitCost   dblNewUnitCost

User · Accepted Answer

Double MAX VALUE is the maximum value a double can represent  somewhere around 1 7 10 308    This should end in some calculation problems  if you try to subtract the maximum possible value of a data type    Even though when you are dealing with money you should never use floating point values especially while rounding this can cause problems  you will either have to much or less money in your system then

User · Answer

this states that Account deposit Double MAX VALUE   it is setting deposit value to MAX value of Double dataType to procced for running tests

User · Answer

Resurrecting the dead here  but just in case someone stumbles against this like myself  I know where to get the maximum value of a double  the  more  interesting part was to how did they get to that number   double has 64 bits  The first one is reserved for the sign   Next 11 represent the exponent  that is 1023 biased   It s just another way to represent the positive negative values  If there are 11 bits then the max value is 1023   Then there are 52 bits that hold the mantissa   This is easily computed like this for example   public static void main String   args         String test   Strings repeat  1   52        double first   0 5      double result   0 0      for  char c   test toCharArray              result    first          first   first   2             System out println result      close approximation of 1     System out println Math pow 2  1023     1   result        System out println Double MAX VALUE         You can also prove this in reverse order        String max    0    Long toBinaryString Double doubleToLongBits Double MAX VALUE         String sign   max substring 0  1       String exponent   max substring 1  12      11111111110     String mantissa   max substring 12  64        System out println sign      0 - positive     System out println exponent      2046 - 1023   1023     System out println mantissa      0 99999   8

[java] Java double.MAX_VALUE?

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