JAVA 基础心得4

最新推荐文章于 2023-01-15 14:51:40 发布

原创最新推荐文章于 2023-01-15 14:51:40 发布 · 832 阅读

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文章标签：

#java #thread #compiler #class #methods #file

本文探讨了Java中类的继承机制及错误的包声明可能导致的问题，并深入讲解了线程间的互斥锁机制，包括如何获取对象级别的锁以及解释了线程调度算法的平台依赖性。

File P1.java

package MyPackage;

class P1{

void afancymethod(){

System.out.println("What a fancy method");

}

//File P2.java

public class P2 extends P1{

public static void main(String argv[]){

P2 p2 = new P2();

p2.afancymethod();

}

1) Both compile and P2 outputs "What a fancy method" when run
2) Neither will compile
3) Both compile but P2 has an error at run time
4) P1 compiles cleanly but P2 has an error at compile time

The package statement in P1.java is the equivalent of placing the file in a different directory to the file. P2.java and thus when the compiler tries to compile P2 an error occurs indicating that superclass P1 cannot be found.

Which of the following statements about threading are true?

1) You can only obtain a mutually exclusive lock on methods in a class that extends Thread or implements runnable.
2) You can obtain a mutually exclusive lock on any object.
3) A thread can obtain a mutually exclusive lock on an object by calling a synchronized method of that object.
4) Thread scheduling algorithms are platform dependent.
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