在Java-8中重构多个If语句 [英] Refactor multiple If' statements in Java-8

问题描述

我需要验证班级中的必填字段

I need to validate mandatory fields in my class

例如， 9 字段不得 null 。

我需要检查它们是否全为空，但我现在使用多个if语句，如下所示：

I need to check if they are all null but I am using multiple if statements for this now as below:

StringBuilder mandatoryExcessFields = new StringBuilder(MANDATORY_EXCESS_FIELDS.length);

if(Objects.isNull(excess.getAsOfDate())){
    mandatoryExcessFields.append(MANDATORY_EXCESS_FIELDS[0]);
}

if(StringUtils.isEmpty(excess.getStatus())) {
    mandatoryExcessFields.append(MANDATORY_EXCESS_FIELDS[1]);
}

if(Objects.isNull(excess.getLimit())) {
    mandatoryExcessFields.append(MANDATORY_EXCESS_FIELDS[2]);
}

if(!Objects.isNull(excess.getLimit()) && Objects.isNull(excess.getLimit().getId())) {
    mandatoryExcessFields.append(MANDATORY_EXCESS_FIELDS[3]);
}

if(!Objects.isNull(excess.getLimit()) && Objects.isNull(excess.getLimit().getAsOfDate())) {
    mandatoryExcessFields.append(MANDATORY_EXCESS_FIELDS[4]);
}

if(Objects.isNull(excess.getExposure())) {
    mandatoryExcessFields.append(MANDATORY_EXCESS_FIELDS[5]);
}

if(!Objects.isNull(excess.getExposure()) && Objects.isNull(excess.getExposure().getCoordinates())) {
    mandatoryExcessFields.append(MANDATORY_EXCESS_FIELDS[6]);
}

if(!Objects.isNull(excess.getExposure()) && Objects.isNull(excess.getExposure().getValue())) {
    mandatoryExcessFields.append(MANDATORY_EXCESS_FIELDS[7]);
}

if(StringUtils.isEmpty(excess.getLimitValue())) {
    mandatoryExcessFields.append(MANDATORY_EXCESS_FIELDS[8]);
}

我们是否有更好的方法来减少此样板代码或任何设计模式或我可以利用Java-8的任何新功能吗？

Do we have a better approach to reduce this boilerplate code or any design pattern or any new feature from Java-8 which I can leverage?

推荐答案

所有 Object.isNull 可能会替换为可选对象及其方法。让我们举例说明这一行：

All the Object.isNull might be replaced with Optional object and its methods. Let's take example the line:

if (!Objects.isNull(excess.getLimit()) && Objects.isNull(excess.getLimit().getId())) {
    mandatoryExcessFields.append(MANDATORY_EXCESS_FIELDS[3]);
}

将简化为（并且在1行压缩仍然可读）：

Would be simplified to (and squeezed on 1 line remains readable):

Optional.ofNullable(excess.getLimit())                                // check the Limit
        .map(limit -> limit.getId())                                  // if not null, getId
        .ifPresent(i -> builder.append(MANDATORY_EXCESS_FIELDS[3]));  // Append if present

对于 String.isEmpty（s）检查，您必须以这种方式创建可选：

And for the String.isEmpty(s) check, you have to create Optional in this way:

Optional.ofNullable(excess.getStatus()).filter(s -> !StringUtils.isEmpty(s))

---

一种简短的方法是将这些 Optional 对象传递到地图中并使用索引迭代它们并执行一个动作。 int count 是多项检查：

---

A short way would be to pass those Optional object into the map and use the index to iterate through them and perform an action. int count is a number of checkings:

Map<Integer, Optional<?>> map = new HashMap<>();
map.put(...);
map.put(1, Optional.ofNullable(excess.getStatus()).filter(s -> !StringUtils.isEmpty(s)));
map.put(...);
map.put(3, Optional.ofNullable(excess.getLimit()).map(limit -> limit.getId()));
map.put(...);

for (int index=0; index<count; index++) {
    map.get(index).ifPresent(any -> mandatoryExcessFields.append(MANDATORY_EXCESS_FIELDS[index]));
}

并且for-cycle也可以简化：

And the for-cycle might be simplified as well:

IntStream.range(0, count).forEach(index -> 
    map.get(index)
       .ifPresent(any -> mandatoryExcessFields.append(MANDATORY_EXCESS_FIELDS[index])));

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