Java8 Optional优雅空值判断的示例代码

public static void implement(User user) throws Exception {
//        原始 ---> 01
        before01(user);
//        优化 ---> 01
        upgrade01(user);
    }

    public static String before01(User user) throws Exception {
//        if(user!=null){
//            if(user.getAddress()!=null){
//                Address address = user.getAddress();
//                if(address.getName()!=null){
//                    return address.getName();
//                }
//            }
//        }
//        throw new Exception("取值错误");
        if (null != user && null != user.getAddress() && null != user.getAddress().getName()) {
            return user.getAddress().getName();
        }
        throw new Exception("取值错误");
    }

    public static String upgrade01(User user) throws Exception {
        return Optional.ofNullable(user)
                .map(user1 -> user1.getAddress())
                .map(user2 -> user2.getName())
                .orElseThrow(() -> new Exception("取值错误"));
    }

public static void before02(User user){
        if (null != user){
            test();
        }
    }

    public static void upgrade02(User user){
        Optional.ofNullable(user).ifPresent(user1 -> test());
    }

public static User before03(User user) throws Exception{
        if(user!=null){
            String name = user.getName();
            if("King".equals(name)){
                return user;
            }
        }else{
            user = new User();
            user.setName("King");
            return user;
        }
        throw new Exception("取值错误");
    }

    public static void upgrade03(User user){
        Optional.ofNullable(user)
                .filter(user1 -> "King".equals(user.getName()))
                .orElseGet(() -> {
                    User user2 = new User();
                    user2.setName("King");
            return user2;
        });
    }