finalize

final ：用于声明属性, 方法和类，分别表示属性不可变、方法不可覆盖、被其修饰的类不可继承。 finally ：异常处理语句结构的一部分，表示总是执行。 finalize ：Object 类的一个方法，在垃圾回收器执行的时候会调用被回收对象的finalize()方法。JVM不保证此方法总被调用。 举例： 修改被final修饰的属性nickName public class Student{ public static void main(String[] args) { final String nickName ="Jack"; nickName = "Jack Ma"; } } 运行结果 Error:(27, 5) java: 无法为最终变量nickName分配值 由此说明被final 修饰的属性是不可变的。 那么，final 修饰的方法setName()是否可以被重写呢？ class Person { private String name; public final void setName(String name){ this.name = name; } } public class Student extends Person{ // 重写被final 修饰的setName()方法 public void setName(String name){ System

I'm new in Java with some background in C++ in my High School years. Now I'm trying to make something and I chose Java as the programming language. I've done my homework and look a lot about "destructors" for Java, finalize() method, and close() or shutdown() methods. But still I think I don't have the idea of how this should work (more info below of course) OK, the concrete question would be why do I need to call close() or shutdown() methods? In my particular case I'm working with a class that I didn't develop that handles a smart card reader, but I've seen that the case of file management,

Javadoc 8 for PhantomReference states: Phantom references are most often used for scheduling pre-mortem cleanup actions in a more flexible way than is possible with the Java finalization mechanism. So I tried creating a thread that is calling the close() method of a Test Object that is eligible for garbage collection. The run() tries to get all Test Objects pre-mortem . Actually the retrieved Test Objects are all null . The expected behavior is, that the Test Objects are retrieved and the close method is called. No matter how many Test Objects you create there is not a single Test Object that

Java has the finalize block which allows to execute some statements after a block is left (executed even if an exception is raised). Example: try { ... } catch (Exception e) { ... } finally { ... // any code here } Ada has the controlled objects which allows to implement a Finalize operation but there is no finalize block equivalent as in java. This is useful for logging, closing files, transactions and so on (without having to create a specific tagged type for each possible block). How would you implement such finalize block in Ada 2005 (while keeping the code readable)? Are there plans in

So, I recently discovered the finalize method in Java (not sure why I missed it before, but there it is). This seems like it could be the answer to a lot of the issues I'm working with, but I wanted to get a bit more information first. Online, I found this diagram illustrating the process of garbage collection and finalize: A couple of questions: This takes place in a separate thread, correct? What happens if I instantiate a new object during finalize? Is that allowed? What happens if I call on a static method from finalize? What happens if I establish a new reference to the object from within

On our server, we started to have problems with OutOfMemoryError . We analyzed the heap dumps using Eclipse Memory Analysis, and found, that many objects were held to do finalization (about 2/3 of the heap): We found, that it could be some finalize() method blocking. I found several bug reports of this problem ( here or here ), and it always manifested itself in the Finalizer thread stack, that it was blocked somewhere. But in our case, this thread was WAITING: "Finalizer" daemon prio=10 tid=0x43e1e000 nid=0x3ff in Object.wait() [0x43dfe000] java.lang.Thread.State: WAITING (on object monitor)

一、final 1.final用于声明属性、方法和类，分别表示属性不可变，方法不可覆盖类和类不可能被继承（不可能再派生出新的子类）。 final属性：被final修饰的变量不可变。 1）.引用不可变 2）.对象不可变 1.final在定义的时候初始化。 2.final成员变量可以再初始化块中初始化，不能在静态初始化块中初始化。 3.静态final成员变量可以在静态初始化中初始化但不可以在初始化块中初始化。 4.类的构造器中初始化，但静态final成员变量不可以在构造函数中初始化 public class finaltest { public static void main(String[] args) { final StringBuffer stringBuffer=new StringBuffer("hello"); stringBuffer.append(" word"); System.out.println(stringBuffer); }​} 运行结果：hello word public class finaltest { public static void main(String[] args) { final StringBuffer stringBuffer=new StringBuffer("hello"); stringBuffer =new

I am confuse in between system.gc() and finalize() method of java. We can't force to collect garbage object to JVM. We are allow to write both methods in our java code then if both are used for garbage collection, then what is point in providing two methods for garbage collection by java? Please tell me the exact working of both methods and internally how it works? ewernli System.gc() kindly asks the sytem to perform a garbage collection. Javadoc says: Runs the garbage collector. You can not control how "hard" the garbage collector will work. How the garbage collector work internally is VM

final 表示最终的、不可改变的。用于修饰类、方法和变量。final 变量必须在声明时给定初值，只能读取，不可修改。final 方法也同样只能使用，不能重写，但能够重载。final 修饰的对象，对象的引用地址不能变，但对象的属性值可以改变 finally 异常处理的一部分，它只能用在 try/catch 语句中，表示希望 finally 语句块中的代码最后一定被执行（存在一些情况导致 finally 语句块不会被执行，如 jvm 结束） finalize() 是在 java.lang.Object 里定义的，Object 的 finalize() 方法什么都不做，对象被回收时 finalize() 方法会被调用。Java 技术允许使用 finalize() 方法在垃圾收集器将对象从内存中清除出去之前做必要清理工作，在垃圾收集器删除对象之前被调用的。一般情况下，此方法由JVM调用。特殊情况下，可重写 finalize() 方法，当对象被回收的时候释放一些资源，须调用 super.finalize() 。 Java 自学指南 Java 面试题汇总PC端浏览【点这里】 Java知识图谱 Java 面试题汇总小程序浏览，扫二维码 所有资源 资源汇总于公众号 来源： https://www.cnblogs.com/ConstXiong/p/11801045.html