final

java :Why the Local variable should be declared final [duplicate]

由 ∥☆過路亽．° 提交于 2019-12-30 08:55:01
问题 This question already has answers here : Closed 7 years ago . Possible Duplicate: Is there any performance reason to declare method parameters final in Java? Why would one mark local variables and method parameters as “final” in Java? I am using PMD to see the code violations. Inside a webService Method, I have this below code public ServiceRequest getData() { Status status = new Status(); // code } What PMD is suggesting me is that, this local variable status could be declared as final. My

Updating UI / runOnUiThread / final variables: How to write lean code that does UI updating when called from another Thread

由 感情迁移 提交于 2019-12-29 08:12:22
问题 I have been reading up on the UI updating when I found out that, like WinForms, Android need to do UI updates on from the main thread (too bad, I was hoping someone could once and for all solve that irritating problem). Anyways, I need to pass that to the UI thread. Some suggest the use of the runOnUiThread method and that might have worked, if it wasn't for that irritating "final" that then came into play. I have an Interface, with a method I cannot change. It looks like this: @Override

final variable case in switch statement

由 廉价感情. 提交于 2019-12-29 05:46:31
问题 final int a = 1; final int b; b = 2; final int x = 0; switch (x) { case a:break; // ok case b:break; // compiler error: Constant expression required } /* COMPILER RESULT: constant expression required case b:break; ^ 1 error */ Why am I getting this sort of error? If I would have done final int b = 2 , everything works. 回答1: b may not have been initialized and it is possible to be assigned multiple values. In your example it is obviously initialized, but probably the compiler doesn't get to

In Java, what purpose do the keywords `final`, `finally` and `finalize` fulfil?

由 好久不见. 提交于 2019-12-29 02:17:08
问题 In Java, what purpose do the keywords final , finally and finalize fulfil? 回答1: final final can be used to mark a variable "unchangeable" private final String name = "foo"; //the reference name can never change final can also make a method not "overrideable" public final String toString() { return "NULL"; } final can also make a class not "inheritable". i.e. the class can not be subclassed. public final class finalClass {...} public class classNotAllowed extends finalClass {...} // Not

final（最终）

由 旧街凉风 提交于 2019-12-28 06:53:21
例一代码（final ）： package cn.tedu.finalx; public class FinalDemo1 { public static void main(String[] args) { //int i看成引用，加上final之后引用指向的数据无法改变---常量 final int i;//声明 i=2;//初始化 //i++;//i的值不能改变 final int[] arr={1,6,5,9};//不能改变的是arr的地址值 arr[0]=10;//元素值可以改变 //arr.length=10;//数组长度被final修饰不能改变 } } 输出： 1,1 例一代码图（final ）： 例二代码图（final ）： 例三代码图（final ）： 来源： CSDN 作者： 佳乐一百 链接： https://blog.csdn.net/qq_45453185/article/details/103629714

In Java, why can't I declare a final member (w/o initializing it) in the parent class and set its value in the subclass? How can I work around?

由 梦想的初衷 提交于 2019-12-28 04:31:04
问题 In a Java program, I have multiple subclasses inheriting from a parent (which is abstract). I wanted to express that every child should have a member that is set once only (which I was planning to do from the constructor). My plan was to code s.th. like this: public abstract class Parent { protected final String birthmark; } public class Child extends Parent { public Child(String s) { this.birthmark = s; } } However, this seems to not please the Java gods. In the parent class, I get the

Why are all fields in an interface implicitly static and final?

由 我只是一个虾纸丫 提交于 2019-12-27 18:20:42
问题 I am just trying to understand why all fields defined in an Interface are implicitly static and final . The idea of keeping fields static makes sense to me as you can't have objects of an interface but why they are final (implicitly)? Any one knows why Java designers went with making the fields in an interface static and final ? 回答1: An interface can't have behavior or state because it is intended to specify only an interaction contract, no implementation details. No behavior is enforced by

c++之关键字：final与override

由 帅比萌擦擦* 提交于 2019-12-27 06:03:02
说明： final与override脱离了虚函数均无效，所以final与override都是用于修饰虚函数。 一：final final用于修改虚函数不能被重写。 二：override override用于修饰虚函数必须被声明。 举个例子1： class live { public : virtual void sleep ( ) = 0 ; //声明这是一个纯虚函数 } ; class people : public { public : void sleep ( ) override { std :: cout << "sleep()" << std :: endl ; } } 以上编译是OK的overide声明的sleep（）会去检测live的纯虚函数sleep()是否存在，不存在就报错； 举个例子2： class live { public : virtual void sleep ( ) final ; //声明这是不可重写的纯虚函数 } ; class people : public { public : void sleep ( ) { std :: cout << "sleep()" << std :: endl ; //这里就会报错 } } 以上编译是不行的，final什么存虚函数是不可重写的； 来源： CSDN 作者： var.zhou 链接： https:/

Initialize a final variable with “this” in Dart

由 ╄→尐↘猪︶ㄣ 提交于 2019-12-24 19:44:17
问题 I have a class like this: class A extends B { final Property<bool> property = Property<bool>(this); } class Property<T> { Property(this.b); final B b; } But I get an error on this saying: Invalid reference to 'this' expression. I believe I can't access this at that moment, probably because the object reference is not ready yet. So I tried other forms of initializing that variable like: class A extends B { final Property<bool> property; A() : property = Property<bool>(this); } But I get the

Any nice way to make a chain of immutable objects loop around?

由 眉间皱痕 提交于 2019-12-24 10:49:02
问题 This question is an extension of this question. I have a class similar to the following. class HighlightableStructure { private final HighlightableStructure NEXT; HighlightableStructure(HighlightableStructure next) { NEXT = next; } } where a HighlightableStructure points to the next structure to highlight. Sometimes, these HighlightableStructure s loop around and refer to a previous HighlightableStructure , but not the first in the chain. Something like h_1 -> h_2 ->h_3 -> ... -> h_n -> h_2,
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