Basic summary of Java Learning

Variables in 1.java are categorized by data type class:Basic data TypesandReference Data Type(Arrays & Classes &interface)>basic data type integral type:byte(8bit) Short int(Default type)Long(add l/at the end of the valueL) floating point type:float Double(default type) character type:Char(‘ ‘, there must be a single quotation mark to denote the character, JS inside there is no specific requirement) Boolean type:Boolean(evaluates to TRUE or FALSE, as with JS)2. Binary decimal binary octal hexadecimal>Binary: The bottom of the computer is the binary to store, the operation of the>Binary storage at the bottom: positive numbers, negative numbers are stored and calculated in the form of complement (original code, inverse code, complement)>conversion between four types of binary3. Operation of the variable A. Automatic type conversion: Small capacity data types are automatically converted to large-capacity data types ShortS=12; inti = S +2; PS:a byte short char is calculated between the int type!So, s+2, must be int type B. Coercion type conversion: is the inverse process of a, using"()" to achieve a strong turn.

An operator is a special symbol that represents the operation, assignment, and comparison of data.Arithmetic operators:+ - +- * / % ++ --PS:1)/:inti = 12; i = I/5;//i=22)%: The last symbol is only the same as the modulus3) before + +: First +1, after Operation + +: first operation, after +1 4) +: String strings can only be concatenated with other data types, and the result is a string-type  assignment operator:
=  += -= *= /= %=intI=12; I=i*5; I*=5;//Ibid .[Special] Shorts=10; s=s+5;//compile will error, the generated s should be int typeS= ( Short) (s+5);//OKs+=5;//S=s+5, but there is no error in compiling this, it does not change the data type of S

comparison operators (relational operators)
= = > < >= <= instanceof

the difference between ps:== and =
returns a Boolean value after the comparison operation
if (i>1&&i<10) {}//ok
cannot be written as if (1<i<10) {}
logical operators (both ends of the operator are Boolean values)
& && | | ^ ^ (or, same take 0, different take one)!
PS: Distinguish between & and &&, and | | | The difference
When we use, choose &&,| |

bitwise operators (data of numeric types on both ends)
<< >> >>> & | ^ ~ (reverse)
PS:1) Here, move left, move to the right, the twos complement, the final result depends on the binary changes,
2) >&gt, move right, left with the number of sign bits to supplement, the right part of the removal is discarded
3) >>> also indicates right shift, but left unsigned right shift
   
[Example]1. How to convert values of m=12 and n=5
2. Convert 60 to 16 binary output

Ternary operators
(conditional expression)? Expression 1: expression 2;
1) Since it is an operator, a result must be returned, and the data type of the result is the same as the expression type
2) Expression 1 is consistent with the data type of expression 2
3) The use of ternary operators, must be converted to If-else, and vice versa not necessarily
Example: Get a larger value of two numbers; get the maximum of three numbers.
 

Basic summary of Java Learning