什么是C＃和Java之间的主要区别？ [英] What are major differences between C# and Java?

问题描述

我只是想澄清一件事。这不是一个问题，关于哪一个更好，这部分我留给别人来讨论。我不关心它。
我一直在问我面试这个问题，我想了解多一点可能是有用的。

I just want to clarify one thing. This is not a question on which one is better, that part I leave to someone else to discuss. I don't care about it. I've been asked this question on my job interview and I thought it might be useful to learn a bit more.

这是我能想出的：

• Java是平台无关。那么现在你可以说还有就是单项目，所以C＃可以考虑太多，但
  我相信这是一个有点夸张。为什么？那么，当Java的新版本做它是它支持所有平台上同步发售，而另一方面有多少C＃3.0的功能在单执行仍然下落不明？或者是不是真的 CLR 主场迎战的 JRE 中，我们应该比较吗？


• Java不支持事件和委托。据我所知。


• 在Java的所有的方法都是虚拟


• 开发工具：我相信没有作为Visual Studio中这样的工具呢。特别是如果你已经与团队合作的版本，你会明白我的意思。

• Java is "platform independent". Well nowadays you could say there is the Mono project so C# could be considered too but I believe it is a bit exaggerating. Why? Well, when a new release of Java is done it is simultaneously available on all platforms it supports, on the other hand how many features of C# 3.0 are still missing in the Mono implementation? Or is it really CLR vs. JRE that we should compare here?
• Java doesn't support events and delegates. As far as I know.
• In Java all methods are virtual
• Development tools: I believe there isn't such a tool yet as Visual Studio. Especially if you've worked with team editions you'll know what I mean.

请添加其他您认为是相关的。

Please add others you think are relevant.

更新：
只是突然了我的心，Java没有像定制的类，方法等属性还是没有呢？

Update: Just popped up my mind, Java doesn't have something like custom attributes on classes, methods etc. Or does it?

推荐答案

对比的Java 7和C＃3

（Java 7中的某些功能不再赘述，但使用C＃对Java 1-6所有版本的语句的优势已被删除。）

(Some features of Java 7 aren't mentioned here, but the using statement advantage of all versions of C# over Java 1-6 has been removed.)

并非所有的总结是正确的：

Not all of your summary is correct:

• 在Java方法是虚拟的默认的，但你可以让他们最终决定。 （在C＃中他们在默认情况下密封的，但你可以让他们虚拟的。）


• 有很多的IDE的Java，无论是免费的（如Eclipse中，Netbeans的）和商业（例如IntelliJ IDEA的）

• In Java methods are virtual by default but you can make them final. (In C# they're sealed by default, but you can make them virtual.)
• There are plenty of IDEs for Java, both free (e.g. Eclipse, Netbeans) and commercial (e.g. IntelliJ IDEA)

除此之外，（什么在你总结的话）：

Beyond that (and what's in your summary already):

• 泛型两者之间完全不同的; Java泛型是只是一个编译时的绝招（但在那一个有用的）。在C＃和.NET泛型是维持在执行时也和值类型和引用类型的工作，保持适当的效率（如列表＆LT;字节＆GT; 作为字节[] 支持它，而不是盒装的字节数组。）


• C＃不检查了异常


• Java不允许用户定义的值类型的创建


• Java没有运营商和转换重载


• Java没有对迭代器的简单实现
迭代器块

• Java没有像LINQ什么


• 部分原因是由于没有代表，Java没有什么很喜欢匿名方法和lambda前pressions。匿名内部类通常填补这些角色，但clunkily。


• Java没有前pression树木


• C＃不具有匿名内部类


• C＃不具备Java的内部课程可言，其实 - 所有嵌套类C＃像Java的静态嵌套类


• Java没有静态类（不具有的的实例构造函数，并且不能用于变量，参数等）


• Java没有任何等同于C＃3.0匿名类型


• Java没有隐式类型的局部变量


• Java没有扩展方法


• Java没有对象和集合初始化前pressions


• 访问修饰符有所不同 - 在Java中有（目前）的装配没有直接等价的，所以没有内部的知名度理念;在C＃中有没有相当于Java中的默认可见其考虑命名空间（和继承）的


• 在Java和C＃初始化的顺序是微妙的不同（C＃中的链接调用基类的构造函数之前执行变量初始化）


• Java不具有作为语言的一部分;他们获取的约定/设置/是方法


• Java没有不安​​全code
相当于

• 互操作是在C＃比Java的JNI
更容易（和.NET一般）

• Java和C＃有枚举有些不同的想法。 Java的是更面向对象的。


• Java没有preprocessor指令（＃定义，＃如果等在C＃）。


• 的Java没有类似的C＃的 REF 和退出通过引用传递参数


• 的Java没有等效部分类型


• C＃接口不能声明字段


• Java没有无符号整型


• Java有一个十进制类型没有的语言的支持。 （java.math.BigDecimal中提供的东西的如的System.Decimal - 有差异 - 但有没有语言支持）


• Java没有相当于空值类型的


• 拳击在Java中使用predefined（但正常）引用类型与他们特定的操作。拳击在C＃和.NET是一个更透明的事情，由CLR任何值类型的拳击正在创建引用类型。

• Generics are completely different between the two; Java generics are just a compile-time "trick" (but a useful one at that). In C# and .NET generics are maintained at execution time too, and work for value types as well as reference types, keeping the appropriate efficiency (e.g. a List<byte> as a byte[] backing it, rather than an array of boxed bytes.)
• C# doesn't have checked exceptions
• Java doesn't allow the creation of user-defined value types
• Java doesn't have operator and conversion overloading
• Java doesn't have iterator blocks for simple implemetation of iterators
• Java doesn't have anything like LINQ
• Partly due to not having delegates, Java doesn't have anything quite like anonymous methods and lambda expressions. Anonymous inner classes usually fill these roles, but clunkily.
• Java doesn't have expression trees
• C# doesn't have anonymous inner classes
• C# doesn't have Java's inner classes at all, in fact - all nested classes in C# are like Java's static nested classes
• Java doesn't have static classes (which don't have any instance constructors, and can't be used for variables, parameters etc)
• Java doesn't have any equivalent to the C# 3.0 anonymous types
• Java doesn't have implicitly typed local variables
• Java doesn't have extension methods
• Java doesn't have object and collection initializer expressions
• The access modifiers are somewhat different - in Java there's (currently) no direct equivalent of an assembly, so no idea of "internal" visibility; in C# there's no equivalent to the "default" visibility in Java which takes account of namespace (and inheritance)
• The order of initialization in Java and C# is subtly different (C# executes variable initializers before the chained call to the base type's constructor)
• Java doesn't have properties as part of the language; they're a convention of get/set/is methods
• Java doesn't have the equivalent of "unsafe" code
• Interop is easier in C# (and .NET in general) than Java's JNI
• Java and C# have somewhat different ideas of enums. Java's are much more object-oriented.
• Java has no preprocessor directives (#define, #if etc in C#).
• Java has no equivalent of C#'s ref and out for passing parameters by reference
• Java has no equivalent of partial types
• C# interfaces cannot declare fields
• Java has no unsigned integer types
• Java has no language support for a decimal type. (java.math.BigDecimal provides something like System.Decimal - with differences - but there's no language support)
• Java has no equivalent of nullable value types
• Boxing in Java uses predefined (but "normal") reference types with particular operations on them. Boxing in C# and .NET is a more transparent affair, with a reference type being created for boxing by the CLR for any value type.

这并不详尽，但它涵盖了所有我能想到的副手的。

This is not exhaustive, but it covers everything I can think of off-hand.

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