使用Java 8中的Lambda的List中的double值的总和

Question

我想遍历帐户列表,并使用Java 8 lambda功能总结Double信用额度.有任何想法吗？

import lombok.*;
import java.util.List;

@Data
public class Account {

private Double amount;
@Getter(AccessLevel.NONE)
private Boolean active;
private String companyCode;
private Long accountNumber;

    public Boolean isActiveAccount() {
        return active;
    }
}

我有一个帐户列表,我想使用Lambda Java 1.8功能总结信用额度,我该怎么做,而不是我在下面显示的传统方法？

//Lets pretend that the list has 3000 account-elements.
List<Account> accountsList = new ArrayList<>();

Double totalAmount = 0.0;

for (Account account : accountsList) {
    Double accAmountList = account.getAmount();
    if(null != accAmountList) totalAmount += accAmountList;
}

Answer 1

从列表中创建一个流,映射到double值列表

total=accountList.stream()
.filter(account ->account!=null&& 
account.getAmount()!=null).mapToDouble(Account::getAmount)
.sum()