Java - 如何在对象列表中搜索值

Question

例如我有列表、类和方法：

List<Client> myClient = new ArrayList<>();

public class Client {
    String firstName;
    String lastName;
    String cID;
    boolean subscription = false;
}

public String activateSubscription(String customerID){
    for( Client myCustomer: myClient ){
        if( myCustomer.cID == customerID ){
            myCustomer.setSubscription();
            break;
        }
    }

    return null;
}

public void getClientName(String customerID){
    String nameCustomer = null;

    for( Client myCustomer: myClient ){
        if( myClient.clientID == customerID ){
            nameCustomer = myCustomer.getFullName();
            break;
        }
    }

    return nameCustomer;
}

public int getNumberOfSubsrtipion(){
    int count = 0;

    for( Client myCustomer: myClient ){
        if( myCustomer.getSubscription ){
            count += 1;
        }
    }

    return count;
}

我是 Java 新手，我想知道是否可以简化这段代码？

也许有更简单的方法来统计订阅客户并通过 ID 搜索客户？

Answer 1

使用

Streams

你可以简化它是的

public long getNumberOfSubscription() {
    return myClient.stream().filter(Client::getSubscription).count();
}

public void activateSubscription(String customerID) {
    myClient.stream().filter(c -> c.getcID().equals(customerID))
            .findFirst()
            .ifPresent(client -> client.setSubscription(true));
}

public String getClientName(String customerID) {
    try {
        return myClient.stream().filter(c -> c.getcID().equals(customerID))
                .findFirst()
                .orElseThrow().getFullName();
    } catch (Exception e) {
        return null;
    }
}