Java基础知识与并发安全-优快云博客

本文链接：https://blog.youkuaiyun.com/qq_30197057/article/details/107565688

本文探讨了Java中不可变对象在并发应用中的重要性，如何使用Collections Framework创建映射键到值的类，并深入理解抽象类、多态、final关键字的作用。此外，还介绍了Object.wait()方法的功能、防止类被继承的方法、高效字符串连接方式以及序列化和静态嵌套类的特性。同时，讲解了synchronized关键字用于保证线程安全，以及如何将Integer数组转换为List，LinkedHashSet的用途，以及重载方法的定义。最后，提到了无符号类型char以及在多线程环境下安全的Map实现——ConcurrentHashMap。

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What are immutable objects most useful in?
Concurrent applications
How do you create a new class that maps keys to values using the Collections Framework?
Extend from AbstractMap to implement the Map interface
Given:
public abstract class Animal{…}
public class Dog extends Animal{…}
What allows you to use a parent class reference to refer to a child class object? For example:
Animal animal = new Dog();

Polymorphism 多态 /,pɒlɪ’mɔːfɪz(ə)m/

What effect does declaring a method as final have?
The method cannot be overridden in subclasses.
What does the Object.wait() method do?
Causes the current thread to wait
How can you stop your class from being inherited by another class?
Declare the class as final.
Between the following options, which is the most efficient way to concatenate a large number of strings in Java?
The append() method in the StringBuilder class.
Which statement is true about destructors in Java?
They are indirectly interpreted as a method called finalize, called at the discretion of the garbage collector.

An abstract class can implement an interface without implementing any of its methods.

Which statement about abstract classes is true?
An abstract class can implement an interface without implementing any of its methods.
Which statement is true about serialization?
When an object is serialized, it is converted into a byte stream.
Which statement about static nested classes is true?
They cannot invoke non-static methods of its enclosing class.
What does the synchronized keyword on a method do?
It uses the object’s intrinsic lock to prevent two threads from accessing any synchronized method of the object simultaneously.
What is the class for mutable sequences of characters Java provides called?
StringBuffer

14.How do you convert an array of type Integer (Integer[]) to a List of type Integer (List)?
By using the static Arrays.asList method

What is a LinkedHashSet?
A hash set which preserves the order in which objects were inserted
When is a method considered to be overloaded?
If it has multiple call signatures within the same class scope
Which primitive type is unsigned?
char
Which Map implementation is safe for modification in a multi-threaded program?
java.util.concurrent.ConcurrentHashMap

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