I cannot add two BigDecimal objects

Question

When I want to add two BigDecimal objects together

public void addBalanceWallet(BigDecimal balanceWallet) {
        this.balanceWallet.add(balanceWallet);
}

There is no effect. Additionally, the IDE shows

Why can't I add these two objects together?

BigDecimal objects are immutable. The result of the addition is returned. You could for example compute `this.balanceWallet = this.balanceWallet.add(balanceWallet);` — President James K. Polk, Sep 30 '21 at 22:30
... and when you add these two values together what would you like to do with the sum? — PM 77-1, Sep 30 '21 at 22:30
I am increasing the balance of the user's wallet. I used BigDecimal because it has high precision, but I can see that it is pointless. — JONKI, Sep 30 '21 at 22:32
Incidentally if this is for Bitcoin you don't need `BigDecimal` at all, because the total outstanding satoshis will never exceed about 2e15, which is less than a Java (signed) `long` can handle by a factor of a thousand, and any single wallet will be even less. — dave_thompson_085, Sep 30 '21 at 22:40
“Immutable” is the very first word in the [Javadoc for `BigDecimal`](https://docs.oracle.com/en/java/javase/17/docs/api/java.base/java/math/BigDecimal.html). — Basil Bourque, Oct 01 '21 at 00:17

score 4 · Answer 1 · answered Sep 30 '21 at 22:32

You are not assigning the return value (which is the actual result of the addition) to anything and thus the "Result (...) is ignored" message. I guess you want to do the following:

public void addBalanceWallet(BigDecimal balanceWallet) {
    this.balanceWallet = this.balanceWallet.add(balanceWallet);
}

score 3 · Answer 2 · answered Sep 30 '21 at 22:32

You have to save the return value. For example:

public BigDecimal addBalanceWallet(BigDecimal balanceWallet) {
        return this.balanceWallet.add(balanceWallet);
}

And afterwards:

BigDecimal addResult = this.balanceWallet.addBalanceWallet(some_big_decimal)

I cannot add two BigDecimal objects

2 Answers2