java - Why is creating an instance of this object altering the instance variable of another object? -

i have defined bankaccount class, , created 2 different accounts extend bankaccount: savings account , checkings account. constructors have posted below:

public class timedepositaccount extends savingsaccount{     private int numberofmonths;     private static final double withdraw_penalty = 20;      timedepositaccount(double interestrate, int numberofmonths){         super(interestrate);         this.numberofmonths = numberofmonths;     } } 

and savings account:

public class savingsaccount extends bankaccount {     private static double interestrate;      public savingsaccount(double interestrate){         super();         this.interestrate = interestrate;     }   } 

in tester create savingsaccount, , timedeposit account:

savingsaccount momssavings = new savingsaccount(5); timedepositaccount collegefund = new timedepositaccount(10, 3); 

after going through debugger, momssavings' interest rate set 5 specified, however, when create collegefund, program changes momssavings' interest rate 10, along creating collegefund object. tell me error is?

thank you.

you've declared interestrate static, there's 1 value across instances.

change non-static:

 private double interestrate;