Combining Two Objects (java)

New to java and I'm confused as to how I can combine these two objects. Sorry if I am not clear / if this has been asked before.

I need to add one.PiggyBank to two.PiggyBank

We are not allowed to change the program used to output the code

    public class PiggyBank {
doubles pennies, nickels, dimes, quarters, totalValue, bankTotal;
public PiggyBank(int p, int n, int d, int q)
{
pennies = p;
nickels = n;
dimes = d;
quarters = q;
totalValue = pennies + nickels + dimes + quarters;
}
public void addPenny()
{
}
//accessors
public double getP()
{
return pennies;
}
public double getN()
{
return nickels;
}
public double getD()
{
return dimes;
}
public double getQ()
{
return quarters;
}
public double combinePiggy(double bank2)
{
two.
bankTotal = bank1 + bank2;
}
public static void main(String[] args) {
PiggyBank one = new PiggyBank(5, 5, 5, 5);
PiggyBank two = new PiggyBank(2, 3, 4, 1);
System.out.println(“Account 1: “ + one + “\n”);
System.out.println(“Account 2: “ + two + “\n”);
one.combinePiggy(two);
System.out.println(“Account 1: “ + one + “\n”);
System.out.println(“Account 2: “ + two + “\n”);
}
}

You need to create that combinePiggy(PiggyBank) method and then add the values of the parameter to the corresponding values you call this on.

Somewhat abstract and simplified example to get you started (you should do the real thing yourself to have a learning effect):

class Thing {
int x;
int y;
void combine(Thing otherThing) { 
x += otherThing.x; 
y += otherThing.y;
}
}

There is so much wrong with this. First of all, it does not make sense to have those attributes listed as type double.
For example: pennies = 0.5; this makes no sense, as you cannot have half a penny in a piggy bank. This needs to be adjusted for all accessor and mutator methods.

public class PiggyBank {
int pennies, nickels, dimes, quarters;
double bankTotal;
.
.
.
public int getP()
{
return pennies;
}
public int getN()
{
return nickels;
}
public int getD()
{
return dimes;
}
public int getQ()
{
return quarters;
}
}

Additionally, the combinePiggy method should not have a return type, as you are not returning anything. Furthermore, as the main method suggests, the combinePiggy method should have another piggybank as a parameter. The method should then add the number of each piggy bank together, as well as the total of each bank.

public void combinePiggy(PiggyBank bank2)
{
pennies += bank2.pennies;
nickels += bank2.nickels;
dimes += bank2.dimes;
quarters += bank2.quarters;
bankTotal += bank2.bankTotal;
}

Another thing, judging by the main method, your class needs a toString method. A toString method is exactly what the name implies. It converts an object into a string. (I'll leave it for you to write the appropriate toString to fit your main method)

  public String toString(){
return "This piggy bank has " + pennies + " pennies, " + nickels + " nickels, " + 
dimes + " dimes, " + quarters + " quarters.";
}

Also, you cannot just add the number of coins in order to get a bank total. Example: You have a penny, a nickel, a dime and a quarter. 0.01+0.05+0.10+0.25=0.41. The way you are doing it, you're bank total would just add up the number of coins.

  public PiggyBank(int p, int n, int d, int q)
{
pennies = p;
nickels = n;
dimes = d;
quarters = q;
bankTotal = pennies*0.01 + nickels*0.05 + dimes*0.1 + quarters*0.25;
}

I think I've done more than answer your question. I will leave the addPenny as well as the setter methods to you. It seems you are very new to Java. I suggest you watch a few videos and read some documentation about the language before you tackle this assignment. Here is a video that more or less sums up the language.