Core Java Interviewfragen und Antworten
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Frage 211. How are Observer and Observable used?
Objects that subclass the Observable class maintain a list of observers. When an Observable object is updated it invokes the update() method of each of its observers to notify the observers that it has changed state. The Observer interface is implemented by objects that observe Observable objects.
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Frage 212. How does Java handle integer overflows and underflows?
It uses those low order bytes of the result that can fit into the size of the type allowed by the operation.
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Frage 213. To what value is a variable of the String type automatically initialized?
The default value of an String type is null.
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Frage 214. What is the range of the short type?
The range of the short type is -(2^15) to 2^15 - 1.
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Frage 215. What is Downcasting ?
Downcasting is the casting from a general to a more specific type, i.e. casting down the hierarchy
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Am hilfreichsten laut Nutzern:
- How could Java classes direct program messages to the system console, but error messages, say to a file?
- What are the differences between an interface and an abstract class?
- Why would you use a synchronized block vs. synchronized method?
- How can you force garbage collection?
- What are the differences between the methods sleep() and wait()?