C#

Reference types are nullable by default; in-language null keyword is untyped. Lack of discriminated unions Exceptions as default, non-exceptional error handling method - there's not much of an alternative. archaic switch statement syntax and limitations Needless distinction between constructors + static methods Static methods can't be part of an interface Lack of by-shape interface implementation rather than explicit interface implementation - leading to numerous language design hacks such as the linq query syntax, foreach, collection & object initializers -- none of which can be flexibly reused. For example, the object initializer syntax may be nice, but plays poorly with immutable objects. Cannot inherit "interface" of a class independently of implementation - leading to code duplications and overarchitected code that provides interfaces, abstract base classes, a few common implementations, and no way to pick and choose the bits of each to use. Also; leads to too many code that's tightly coupled to a particular implementation since it's common to explicitly refer to the implementation type rather than an interface. Cannot multiply inherit via composition since a classes "interface" is tightly coupled to it's implementation; effectively lack of mixins. The above limitations of interfaces lead to a proliferation of virtually identical interfaces that don't overlap naturally in any kind of type hierarchy. IComparable vs. IEquatable vs. IComparable<T> vs object.Equals vs. operator == etc. etc. By extension, making a custom type that satisfies all these things is a lot more work than necessary (in particular for collection classes). Obviously, the language designers realize this, hence the various workarounds for things like linq, foreach and collection initializers which work by-shape rather than by-interface. Redundant use of parentheses and braces rather than layout-is-structure. Return values can be ignored, limiting the effectiveness of type inference. Enums aren't a normal type and can't have methods. Also, enum values aren't typesafe and may be initialized to 0 despite not having a 0 value. Mixing metaphors by lumping flag and non-flag enums together. Lack of proper value type support. Value types can't be inherited, have different constructor semantics, and perform poorly due to CLR limitations. Also, confusing semantics regarding value types: some values are really values (and can't be modified), and others are really non-aliased, non-null references (variables). This gets particularly confusing with regards to the next issue: Semantic distinction between fields and properties, particularly in conjunction with lack of mutability modifier (ala C++'s const) Can't specialize generics Cannot provide default generic type parameters (e.g. factory generics) lack of typedef makes generics a pain to use (using is a limited but good-to-know substitute!) Can't genericize over things other than types (e.g. functions, plain values, or names). This means you can't do something like make a generic implementation of a dependancy property leading to, well, nasty implementations of things like dependancy properties and the overuse of code-snippets and poorly readable code as a result. Limited capability to specify generic type requirements e.g. generic sum method that takes both int, double and a bigint (without tricky and often slow hacks). An interface method implementation or virtual method override cannot return a more specific type or accept a more general type; i.e. limited co/contravariance support even in C# 4.

C++

The inconsistencies in the libraries related to char* and std::string. All C++ libs should take std::strings. Characters are not bytes with respect to iostream. I do a lot of byte-oriented work. Having a "byte" type and a "character" type would significantly make it simpler. That, too, would permit scaling to Unicode somewhat easier. Bit operations should be easy on a value. I should be able to access and set the n'th bit of a value without playing AND/OR dancing. The lack of a standardized interface for GUIs. This is where Microsoft has really been able to position themselves well with C#. A standard interface binding that OS makers provide would go really far for my work.

objective - c

1)没有命名空间，只有手动命名约定——我不介意在类分离方面，但我确实怀念能够在一行命名空间中导入所有类定义(如import com.me.somelibrary.*)。

2)库在像RegEx支持这样的重要领域仍然存在一些漏洞。

3)属性语法有点笨拙，需要三行(在两个单独的文件中)来声明一个属性。

4)我喜欢保留/释放模式，但它比应该的更容易释放一个引用，然后意外地使用它。

5)虽然不是真正的语言特性，但Xcode与Objective-C的使用是如此交织在一起，我不禁想到这方面……基本上自动补全，是很可疑的。它更像是一个奖励你找到你想要的东西的系统，然后把它作为一个选择。但我想我从来都不喜欢自动补全引擎。

C / C + +

缺乏完整的SWAP功能 模板的语法 你不能#define一个#define(没有多通道) 编译器之间的结构打包不兼容 Char是有符号的还是无符号的?

Java

边缘上的不变性 没有像c#一样的ref关键字 到处尝试/捕捉积木 运行时性能差 所有与字符串相关的东西

Python

没有“main”(我已经习惯了!) 强调关键词 有限的线程支持 用self代替this 缺少类似C/ c++的语法

C#

当被枚举的集合中的对象发生变化时，foreach命令弹出， UI控件吐出假人，因为它们在错误的线程上访问。当然是所有的调度员。调用可以移动到CLR管道， PInvoke，编组等， 我浪费了两年时间学习远程遥控， 它没有露比性感。

我讨厌Java(目前它是我最喜欢的语言)的五个方面，排名不分先后。

As much as I am a fan of Java Generics, there are a lot of oddities that arise from the way it was designed. As such there a myriad of annoying limitations with generics (some of which are the result of type-erasure). The way Object.clone() and the Cloneable interfaces work is totally broken. Instead of taking the high-road and making everything an object (a.la. SmallTalk), Sun wimped out created two distinct categories of data-types: Objects and primitives. As a result there are now two representations for fundamental data types and wierd curiosities such as boxing/unboxing and not being able to put primitives in a Collection. Swing is too complex. Don't get me wrong: there's a lot of cool stuff one can do with Swing but it is a great example of over-engineering. This final complaint is equally the fault of Sun and those whom have written XML libraries for Java. Java XML libraries are way too complicated. In order to simply read in an XML file, I often have to worry about what parser I am using: DOM or SAX? The APIs for each is equally confusing. Native support in the language for easily parsing/writing XML would be very nice. java.util.Date sucks. Not only is it unnecessarily complicated but all the useful methods have been deprecated (and replaced with others that increase complexity).