Character set, and encoding the string

What is the character set (Charset)

• A character set is a collection of characters. Generally contains the characters of a language. For example, GBK character set that contains all the commonly used Chinese characters. ASCII is a character set contains English characters.
• Java is a character in the char, char is the character shorthand.

 

What is the encoding (Encoding)

• char represents a character, char is digital in nature. The digital maps to character, called encoding.
• Map one character set to digital, it is to give this character set encoding. Is a standard coding, all computer systems perform in accordance with a coding standard.
• Sometimes coded character sets and mix.

 

Common character sets Introduction

• ASCII code, ASCII table: https://baike.baidu.com/item/ASCII/309296#3
• Unicode includes all commonly used characters in the world, there are several coding, including UTF-8 (8-bit Unicode Transformation Format), UTF-16 and the like.
• Unicode, GBK and all common character sets, will be compatible with ASCII. For example, the character A in all of these conventional character set, the corresponding figures are 65.

 

public class ComplexChar {
    public static void main(String[] args) {
        int a = 65;
        char cha = (char) a;

        char hhh = '\u4239';

        System.out.println(cha);

        System.out.println(hhh);
    }
}

 

 

 

Java set of characters

• Java is used in the UTF-16 encoded Unicode.
• UTF-16 with a 16 bit, i.e., 2 byte, which is the reason the two byte char account. When the char into digital time, needed int.

 

ASCII code, and the escape character (escape character)

• How to output special characters:
  • ASCII code + char, may need to find the corresponding digital character by ASCII table. This number is converted to char, and then outputs the char.
  • Escapes. Escape character is used to assign, which may be used in a string as a character string.
• Escape syntax and common escape character:
  • \ N newline character (new line)
  • \ T Tab
  • \" Double quotes
  • \ UXXXX unicode character encoding corresponding

public class ComplexCharInString {
    public static void main(String[] args) {
        // \t制表符 \"双引号 \n换行（new line）
        String content = "a\tb\"\tc\n\td\t";
        String align = "1111222233334444";
        System.out.println(content);
        System.out.println(align);
    }
}

 

String "addition"

• The variable string is inserted in the output
  • And adding strings may be any type, it will be the value of the character spliced to the string;
  • Strings can also be used + = operator to splice;
  • String addition operator compliance additive operators own priority.
• The basic data types string is not in Java
  • The name is a string type String ;
  • Although the basic data type String is not Java, but also can use a similar syntax: String str = "abc";  to create. Initially it as a basic type, easier to understand.
  • String is not a reserved word in Java.
• String addition does not change the value of the original String variable, use an assignment change its value

public  class StringConcat {
     public  static  void main (String [] args) {
         int String = 999; // String not the basic data types, nor keywords and reserved words. But you can use a similar syntax. 
        System.out.println (String); 

        String zifuchuang = "String declaration string!" ; 
        System.out.println (zifuchuang); 

        int A = 10 ;
         int B = 20 is ;
         int C = A + B; 
        the System. Out.println ( "A + B =" + C); 

        Boolean aBiggerThanB = A> B; 
        System.out.println ("a> b is" + aBiggerThanB + "a." ); 

        System.out.println ( "B + a =" + a + B); // here will be a first character string and the foregoing are connected. 
        System.out.println ( "A + B =" + (A + B)); 
        System.out.println ( "* B = A" + A * B); 
    } 
}

public  class the stringvariable {
     public  static  void main (String [] args) {
         // Although the basic data type String is not Java, but also can use a similar syntax: String str = "abc"; to create. 
        int a = 10 ; 
        String str = "is a value" ; 
        str = str + a; // assignment changes the value of str. 
        System.out.println (STR); 

        String s2 = "is a value" ; 
        System.out.println (s2 + a); // adder itself does not change the value of s2. 
        System.out.println (S2); 
    } 
}