How to use java operators

Four arithmetic operators

The plus sign " " among the four arithmetic operations has three common uses:

1, For numbers, that's addition.

2. For the character char type, before calculation, char will be promoted to int and then calculated. Comparison table between char type characters and int type numbers: ASCII, Unicode

3. For string String (the first letter is capitalized, not a keyword), the plus sign represents the string concatenation operation . When any data type is connected to a string, the result will become a string.

Increase operator:

Decrease operator: --

Basic meaning: Let a variable increase by a number, or make a variable decrease by a number 1

Use the format: write it before the variable name, or write it after the variable name.

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For example:

++num，也可以num++

Usage method:

1. Use alone: Do not mix with any other operations, become an independent step by itself

2. Mixed use; mixed with other operations, such as mixed with assignment, or mixed with printing operations, etc.

Usage differences:

1. When used alone, there is no difference between the front and back. That is to say, the two have exactly the same effect.

2. There is a big difference when used in combination

[Note]

A: If it is [before], then the variable [immediately 1], then get Use the results. [Add first, then use]

B: If it is [Later], then use the original value first, [then let the variable 1]. [Use first, then add]

Notes:

Only variables can use the increment and decrement operators. Constants cannot be changed, so they cannot be used.

Assignment operator

Assignment operator is divided into:

Basic assignment operator: it is an equal sign "=", representing Give the data on the right to the variable on the left.

int a = 30；

Compound assignment operator;

+= a+=3 
相当于 
a=a+3
-= *= /= %= 都是如此

Note:

Only variables can use assignment operators, constants cannot be assigned.

The compound assignment operator implies a forced type conversion.

byte num = 30；
num += 5；
//num = num + 5
//num = byte + int
//num = int + int
//num = int
//num = （byte） int
System.out.println(num);//35

Comparison operators

Greater than: >

Less than: 3ed9a747ebe61342ff8e3ee4464d1630 =

Less than or equal to: <=

Equal: ==

Not equal: !=

Notes:

1 . The result of the comparison operator must be a Boolean value. If it is true, it is true. If it is not true, it is false

2. If multiple judgments are made, they cannot be written consecutively. The way of writing in mathematics, for example: 3

Logical operators

and && are true only if they are all true, otherwise they are false

or || If at least one of them is true, they are all true What is false is false

NOT! Negating

with "&&" or "||" will have a short-circuit effect: if the final result can be determined based on the left hand side, then it will not be executed later, thus saving a certain amount of performance.

Note:

Logical operators can only be used for Boolean values. AND, or two operators, if there are multiple conditions, you can write two conditions continuously: Condition A&& Condition B Multiple conditions: Condition A&& Condition B Condition C

Ternary operator

Unary operator: An operator that only needs one data to operate, for example: negation! , self-increment, self-decrement

Binary operator: An operator that requires two data to operate, for example: addition, subtraction

Ternary operator: One that requires three data Operators that can operate

Format:

数据类型 变量名 = 条件判断 ？ 表达式A ： 表达式B

Process:

First determine whether the condition is established. If it is true, then the value of expression A Assign to the variable on the left. If it is not true, then assign the value of expression B to the variable on the left. Choose one of the two.

Note:

Both expression A and expression B must meet the data type requirements on the left.

int cai = 3>4?3.7:10;//错误写法

The result of the ternary operator must be used.

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