NDK and C language basic syntax (ii)

First, the String class: (Belongs to the class type)-string (only in C + +)

You must learn to introduce the string type before use:

Introduction of String header file (System header File): #include <string> PS: header file is not string.h

1. Definition string: String a= "abc"; String b= "Abd";

2. String comparison: From left to right from the first character, compared to the size of the ASCII code

From the beginning look: A==a,b==b,c>d so a>b;

3. String array: The element string in the string array does not have an end bit such as '/';

Second, constant and variable

1. What is a constant:

Value cannot change the amount of 1 1.2 fixed value

Types of constants:

(1) Numeric constants (integers, floating-point numbers);

(2) Character-type constants (character constants, escaped character constants, string constants)

(3) Symbolic constant (#define constant value of the constant name of the symbol)

2. Variables

(1) Variables

The amount of value that can be changed during program run becomes variable;

Naming rules for variables: C + + Specifies that identifiers can only be composed of letters, numbers, underscores, and can only be case-sensitive by letter and underscore

Keywords and reserved words cannot be used;

(2) Constant variable

Variable with const keyword, program run time value cannot be changed, call constant variable

PS: The constant variable must be initialized at the time of definition, and thereafter his value cannot be changed;

Third, operator

1. Arithmetic operators:

+-*/% + +--

Subtraction dividing the remainder from adding self-subtraction

2. Relational operators:

> < = >= <=! =

Greater than or equal to or less than equals not equal to

The return value is bool (the return value in the C language is 0 and 1)

3. Logical operators:

&& | | ！

Logical AND logical or logical non-

The two values before and after the logical operators are bool (the C language must be 0 and not 0 values);

&&: All true is true, as long as another one is false;

|| : As long as one is true;

！ : Contrary to current;

4, Bitwise operators:

<< >> & | ^           ~

Bitwise LEFT SHIFT bitwise RIGHT SHIFT bitwise VS. bitwise OR bitwise XOR or bitwise REVERSE

Original code anti-code complement

5. Assignment operator =

(1) Meaning: Assigns the value to the right of the assignment operator (including the result of the last operation of the expression) to the variable to the left of the assignment operator;

A=1;

(2) Right binding of assignment operation

NDK and C language basic syntax (ii)