分类: cpp - 成长日记

2022-01-03发表2022-01-03更新cpp1 分钟读完 (大约189个字)

java和c++的区别

java和c++的不同点

BASIS FOR COMPARISON	C++	Java
Memory Management	Managed by developers using pointers. Supports structures and union	Controlled by the system, does not use pointers. Supports Threads and Interfaces
Inheritance	Provide single and multiple inheritances both	Does not support multiple inheritances. Uses the concept of Interface to achieve
Runtime error detection mechanism	Programmer’s responsibility	System’s responsibility
Libraries	Comparatively available with low-level functionalities	Provide a wide range of classes for various high-level services
Program Handling	Methods and data can reside outside classes. The concept of a global file, namespace scopes available	All methods and data reside in the class itself. Concept od Package is used.
Type Semantics	Supports consistent support between primitive and object types	Different from primitive and object types
Portability	Platform dependent as source code must be recompiled for different platform.	It uses the concept of bytecode which is platform-independent and can be used with platform-specific JVM.
Polymorphism	Explicit for methods supports mixed hierarchies	Automatic uses static and dynamic binding

参考文章：https://www.educba.com/c-plus-plus-vs-java/

2022-01-03发表2022-01-03更新cpp4 分钟读完 (大约622个字)

C++中指针和引用的使用

指针和引用的区别

指针是一个持有某个变量内存地址的特殊变量，使用*号表示。

引用类似于指针，一般可以认为是持有某个值的变量的别名，它被用来关联被赋值给它的变量，使用&表示。

引用存储的是变量的地址。

语法层面的区别如下：

	指针	引用
是否可以为null	可以指向一个null	不能为null，否则会报异常
声明方式	使用`*`号声明	使用`&`声明
是否可以级联	可以级联声明 int ptr; int *ptr1; int x = 10; int y = 20; ptr = &x; ptr1 = &ptr;
是否可以重新赋值	可以	一旦变量被赋值给引用变量，那么这个引用变量将不能重新被赋值
是否可以做算术运算	可以	不可以

S.No.	Pointer	Reference
1.	Pointers in C++ can be assigned to NULL values.	References in C++ can never be NULL else; it will throw an exception.
2.	To dereference a variable in the case of pointers, (*) operator is used	There is no need for referencing the variable; the variable name is simply used in case of reference in C++.
3.	Pointers allow multiple levels of indirection, which means that pointer to pointer to pointer assigning and targeting is possible. For example: int ptr, int *ptr1; int x= 10; int y= 20; ptr = &x; ptr1 = &ptr;	No multiple levels of indirection are possible in the case of references. Only a single level is applicable in references. Implementing multiple levels in references in C++ throws a compiler error to the user. For example, int a = 13; int &ref = a; int &&ref1 = ref;
4.	A pointer can be reassigned to point to another variable. But the variable needs to be of the same type of variable. For example: int *p; Int x, y; p = &x; p = &y;	Once the variable is referred to by the reference variable, it cannot be reassigned to refer to another variable.
5.	All the arithmetic operations like addition, subtraction, increment, etc., are possible in the case of pointers in C++. This is known as Pointer arithmetic. For example: int arr [5] = {10, 20, 30, 40, 50}; int p = arr; for (int i =0; i<5; i++) { cout << *p << endl; p++; }	Arithmetic operations are not possible in the case of references. In C++, it will throw a compiler time error when it tries to do so. For example: int x = 10; int &ref = x; cout << ref++ << endl;
6.	In the case of declaring a pointer in a C++ program, () operator is used before the pointer name. For example: int ptr;	In the case of reference, the reference variable is declared by using the (&) operator before the reference variable, which stands for the address. For example: Int a= 10; int &ref = a;
7.	The pointer variable returns the value whose address it is pointing to. Value can be retrieved using the (*) operator.	The reference variable returns the address of the address it is referring to. The address can be retrieved using the (&) operator.
8.	The pointer variable in C++ has its own address in computer memory, and it also occupies space in the stack.	The reference variable does not have its own memory address; instead, it only points to the variable and shares the same address as the original variable.