自分にとってのOptionalの価値は下記と思われる
昔
String result = ""; //初期化
AaaaModel aaaaRec = aaaaMapper.find("the_id");
if(aaaaModel != null){ //null チェック
String title = aaaaRec.getTitle();
if(title != null){ //null チェック
BbbbModel bbbbRec = bbbbMapper.find(title);
if(bbbbRec != null){ //null チェック
String theId = bbbbRe.getId();
if(theId != null){ //null チェック
result = theId ;
}
}
}
}
↓
java8で書く
String result = Optional.ofNullable(aaaaMapper.find("the_id"))
.map(aaaaRec -> aaaaRec.getTitle())
.map(title -> bbbbMapper.find(title))
.map(bbbbRec -> bbbbRec.getId())
.orElse("");