Introduction to Java first quarter chapter III common operators

This is my lesson Web Java course notes, the original video link is: http://www.imooc.com/learn/85

3-1 what is an operator
An operator is a "function" symbol that informs Java about the operation. For example, if we need to set the value of the variable age to 20, we need a "=" to tell the program that it needs to be assigned. The common operators in the Java language can be categorized as follows:? Arithmetic operators
? assignment operators
? comparison operators
? logical operators
? Conditional operators

3-2 arithmetic operators in Java
Arithmetic operators commonly used in Java:

where + + and--can appear on the left side of the operand, or on the right, but the result is different
Example 1:
Operation Result:

Example 2:
Operation Result:

It is important to note that the increment and decrement operators can only be used for operation variables and cannot be used directly to manipulate values or constants! For example, 5++,8--and so on are all wrong.
3-3 assignment operators in Java
Common assignment operators supported by Java, as shown in the following table:


3-4 comparison operators in Java
The common comparison operators in Java are shown in the following table:


Attention! The ①>,<,>=,<= only supports the left and right sides of the operand is Numeric Type②==,! = operands on both sides can be numeric types or reference types.
3-5 logical operators in Java
The logical operators commonly used in Java are shown in the following table:

We can understand logical operators from the perspective of "voting":

1, and : Ask everyone to vote for consent, to pass an issue

2, or : Just ask a person to vote for permission to pass an issue

3, non : Someone originally voted to agree, through the non-operator, you can make their votes invalid

4. xor : There is only one person who can vote to approve the issue.

When using logical operators, we encounter a very interesting " short circuit " phenomenon.

For example: (One > both) && (one < three), if you can determine that the left one > The run result is false, then the system thinks there is no need to execute the one < three on the right.

Similarly, in (One > both) | | (One < three), if you can determine that the left expression will run as true, the system will also assume that it is no longer necessary to perform the one < three on the right.

3-6 conditional operators in Java

The conditional operator (? :) also known as the ternary operator.

Syntax form: boolean expression? Expression 1: Expression 2

Operation procedure: Returns the value of expression 1 If the value of the Boolean expression is true , otherwise returns the value of expression 2

For example:

Because the value of the expression 8>5 is true, the return: 8 is greater than 5

3-7 Precedence of operators in Java
The precedence of operators commonly used in Java is shown in the following table:

Level 1 has the highest priority, and level 11 has the lowest priority . For example, the result of x = 7 + 3 * 2 is 13 "Multiply First and add"!

PS: We don't have to go. The order of precedence of the rote operators, which is typically used to assist in priority management in real-world development. For example:

Analysis: Parentheses have the highest precedence, so

1, execute a + 18, the result is 30

2, perform (A + 18)% 4 modulo, the result is 2

3, execute A * ((A + 18)% 4), the result is 24

Introduction to Java first quarter chapter III common operators