Call by Value and Call by Reference

• Call by value: Method parameters are copied into the parameter variables when a method starts
• Call by reference: Methods can modify parameters
• Java has call by value
• A method can change state of object reference parameters, but cannot replace an object reference with another

  public class BankAccount
  {
     public void transfer(double amount, BankAccount otherAccount)
     {
        balance = balance - amount;
        double newBalance = otherAccount.balance + amount;
        otherAccount = new BankAccount(newBalance); // Won't work
     }
  }