String - String()
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String()
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 String thisString = String(13); gives you the String "13". You can use other bases, however. For example, String thisString = String(13, HEX); gives you the String "D", which is the hexadecimal representation of the decimal value 13. Or if you prefer binary, String thisString = String(13, BIN); gives you the String "1101", which is the binary representation of 13.
語法 String(val) String(val, base) String(val, decimalPlaces)
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
an instance of the String class
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
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