Comparative analysis of the differences between C# and Java

Similar points:

are both object-oriented programming languages, and both can implement object-oriented (encapsulation, inheritance, polymorphism) ideas

Difference:

1. The namespace in c# is similar to the package in Java. To import a package in Java, use import while in c# Use using.

2. Both c# and Java enter from the main function, but the first letter of the main function in c# must be capitalized

3. Data type: Java and c# are basically the same, but Java The first letter of the String type must be uppercase, but in c# it can be lowercase or uppercase, and there is also a boolean type, which is boolean in Java and bool in c#.

4. Naming of variables: The $ symbol can be used in Java, but not in C#.

5. Output: C# has three ways to output: Cosole.WriteLine(); Cosole.WriteLine (value to be output); Cosole.WriteLine ("format string", variable list); The first two The usage is the same as the system.out.println() method in Java. The third method is based on placeholder output, which is more convenient than Java.

6. Control flow statement: C# is similar to Java , and the switch in C# must have a break if there is content behind the case; Java does not need a break;

7. The static final modifier in Java. In C#, constants can be declared using the const keyword.

8. Access modifiers: The access modifiers in C# basically correspond to those in Java, but there is an extra internal. In short, C# has 5 types of accessibility as follows:
public: Members can be accessed from any code. protected: Members can only be accessed from derived classes.

internal: Members can only be accessed from within the same assembly.

protected: Members can only be accessed from derived classes within the same assembly.

private: Members can only be accessed within the current class.

9. Since the final keyword does not exist in C#, if you want a class to no longer be derived, you can use the sealed keyword to seal it.

10. Collection: Both languages ​​have collections ArrayList, and accessing values ​​through keys is HashMap in Java and HashTable in C#. C# is easier than Java's multi-generic collections List and Dictionary. There is no need to unbox and pack them, and it is safer.

11. Inheritance: Java uses the keyword extends, and C# only uses ":". To call the constructor method of the parent class, Java uses the super keyword, while C# uses the base keyword.

12. Polymorphism: Both abstract classes and abstract methods use the abstract keyword. If another class in Java inherits it, it can directly override this method; while in C#, the keyword override must be added to implement it. C# also has one more virtual method than Java to implement polymorphism.

13. Interface: They are all defined with the keyword interface, Java is implemented with the keyword implements; C# is implemented with ":". In C#, all methods within an interface are public methods by default. In Java, a method declaration can have the public modifier (even though this is not required), but in C# it is illegal to explicitly specify the public modifier for an interface method.

14. The is operator in C# is the same as the instanceof operator in Java. Both can be used to test whether an instance of an object belongs to a specific type. There is no equivalent operator in Java to the as operator in C#. The as operator is very similar to the is operator, but it is more "aggressive": if the type is correct, the as operator attempts to convert the object reference under test into the target type; otherwise, it sets the variable reference to null.

15. Declare arrays

In Java, the method of declaring arrays is very flexible. In fact, there are many methods of declaring arrays that are legal methods. For example, the following lines of code are equivalent:

int[] x = { 0, 1, 2, 3 }; 
int x[] = { 0, 1, 2, 3 };

But in C#, only the first line of code is legal, and [] cannot be placed after the variable name.

Thank you everyone for reading, I hope you will benefit a lot.

This article is reproduced from: https://blog.csdn.net/qq_39657909/article/details/80781481

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