“String - String()”的版本间的差异

String()

描述

Constructs an instance of the String class. There are multiple versions that construct Strings from different data types (i.e. format them as sequences of characters), including:

 -  a constant string of characters, in double quotes (i.e. a char array)
 -  a single constant character, in single quotes
 -  another instance of the String object
 -  a constant integer or long integer
 -  a constant integer or long integer, using a specified base
 -  an integer or long integer variable
 -  an integer or long integer variable, using a specified base
 -  a float or double, using a specified decimal palces 

Constructing a String from a number results in a string that contains the ASCII representation of that number. The default is base ten, so

gives you the String "13". You can use other bases, however. For example,

gives you the String "D", which is the hexadecimal representation of the decimal value 13. Or if you prefer binary,

gives you the String "1101", which is the binary representation of 13.

语法

String(val) String(val, base) String(val, decimalPlaces)

参数

val: a variable to format as a String - string, char, byte, int, long, unsigned int, unsigned long, float, double base (optional) - the base in which to format an integral value decimalPlaces (only if val is float or double) - the desired decimal places

返回值

an instance of the String class

示例

All of the following are valid declarations for Strings.

String stringOne = "Hello String";                                     // using a constant String
String stringOne =  String('a');                                          // converting a constant char into a String
String stringTwo =  String("This is a string");                 // converting a constant string into a String object
String stringOne =  String(stringTwo + " with more"); // concatenating two strings
String stringOne =  String(13);                                          // using a constant integer
String stringOne =  String(analogRead(0), DEC);          // using an int and a base
String stringOne =  String(45, HEX);                                // using an int and a base (hexadecimal)
String stringOne =  String(255, BIN);                               // using an int and a base (binary)
String stringOne =  String(millis(), DEC);                        // using a long and a base
String stringOne =  String(5.698, 3);                                // using a float and the decimal places