如何使用增强的 for 循环更改方法，该方法将方法调用返回到 Java 中的 Stream？

Question

I have a method called getBalance where I have an enhanced for loop and inside the loop I return customer.getBalance();

I now want to change that method in to a Stream from Java 8 and I can't figure out how to do it since you cannot return something inside a stream.

The method:

public double getBalance(String personalNumber, int accountNumber) {

    for (Customer customer : customers) {
        if (customer.getPersonalNumber().equals(personalNumber)) {
            return customer.getBalance(accountNumber);
        }
    }
    return 0;
}

Answer 1

You can do that using filter and findFirst :

return customers.stream()
        .filter(customer -> customer.getPersonalNumber().equals(personalNumber))
        .findFirst()
        .map(customer -> customer.getBalance(accountNumber))
        .orElse(0);