參考鏈接https://stackoverflow.com/questions/41590134/null-safe-collection-as-stream-in-java-8
在操作集合的時候經常寫類似這樣的代碼來防止出現集合爲空的情況:
public void streamOp(List sourceList) {
if (sourceList == null) {
sourceList = new ArrayList();
}
// ...
}
其實有更簡潔的寫法:
public void streamOp(List sourceList) {
Optional.ofNullable(sourceList).orElse(Collections.emptyList());
// ...
}