Java Lambda表达式(3) - 建议用法与示例
2018-07-12
Coding
Lambda
Java
👋 ️️阅读
❤️ 喜欢
💬 评论
🖨️ 打印
Java Lambda表达式(3) - 建议用法与示例
Hints
- Only use method ref on final variable. (NPE in method reference will be confused in debug)
- With rule 1, use method ref rather than lambda
- Only use input arguments in lambda as far as possible
- Be careful of
thisreference, in both lambda and method reference - With rule 1-4, use lambda rather than anonymous class
Samples
this escape
class Domain{
StringProperty name = ...;
}
class UI {
void init () {
domain.name.addListener((ob, o, n) -> updateNameColumn()); // Don't do this, domain will hold this reference
}
}
domain.name.addListener(weak(this, (obj, o, n) -> obj.updateNameColumn())) // Do this, it only capture weak reference of this
Capture wrong instance
class UI {
Session session;
void initEvent(){
EventBus.observe(MaskEvent.class)
.filterSource(session::containsMask) // Don't do this, session is changeable, unless you really only care about session in this moment.
}
void bind(Session newSession){
session = newSession;
}
}
.filterSource(source -> session.containsMask(source)) // Do this, it will check in current session
Avoid capture this
class GetLineHelper {
final File file;
final ByteBuffer buffer;
final List<String> result;
IntFunction<String> lineGetter(){
return i -> result.get(i); // Dont' do this, it capture `this`.
}
}
IntFunction<String> lineGetter(){
return result::get; // Do this, it capture result only.
}
// If it can't represent as method reference, you can let the final field be a local variable and then capture it.
IntFunction<String> lineGetter(){
List<String> result = this.result;
return i -> {
LOGGER.debug("get line " + i);
return result.get(i);
};
}