- 2021-03-31 21:52
*views 2*- Self increasing and self decreasing oper
- Short circuit and
- javase
- operator
- Java
- ternary operato

<>1 operator

<>1.1 summary

operator For connecting expression Of Operands , And perform the operation on the operands .

for example , expression num1+num2, Its operands are num1 and num2, The operator is ”+”.

stay java In language , Operators can be divided into 5 Types ：

Arithmetic operator , Assignment Operators , Relational operators , Logical operators , Bitwise Operators .

Depending on the number of operands , Operators are divided into monocular operators , Binocular and trinary operators .

The unary operator has only one operand , The binocular operator has two operands , The ternary operator has three operands .

Bit operators involve binary bit operations , stay java Not many of them are used in the procedure .

<>1.2 Operator quick reference table

<>1.3 practice ： Test self increase and self decrease

create package : cn.tedu.basic

Create class : TestOperator.java

package cn.tedu.basic; /** This class is used to test the remainder and auto increment auto decrement operators */ public class TestOperator{

//0. Create entry function /**main Alt+/ Complete code ,Ctrl+s preservation Ctrl+F11 implement */ public static void main(

String[] args) { /** Four operations + - * / */ /**syso Alt+/ Complete code */ //2. Test division and remainder % System.

out.println(25/10);//int/int->int, Shang is 2 System.out.println(25 % 10);// model , Mod

//3. Test the add subtract operator /** Prefix form , The symbol comes first , Transform first , Reuse ++a --a * Suffix form , Symbol after , Use first , Change again a++ a-- * ++: plus 1

--: reduce 1 * */ int a = 1; System.out.println("*************"); System.out.println(a

++);// The print result is 1, Change after printing , Self accretion 2 System.out.println(a); int b = 1; System.out.println(

++b);// The print result is 2, Because symbols come first , First increase int c = 1; System.out.println(c--);

// The print result is 1, Symbol after , Print first , Further self subtraction System.out.println(c);// After subtraction, it becomes 0 int d = 1; System.out.

println(--d);// The print result is 0, Symbol before , Subtract before printing // Because of the influence of the previous code ,c The initial value of is 0 System.out.println(--c-c-

c--);//-1-(-1)-(-1)=-1+1+1=1 System.out.println(c);//-2 } }

<>1.4 practice ： Finding the maximum of two numbers

create package : cn.tedu.basic

Create class : TestMaxNum.java

package cn.tedu.basic; import java.util.Scanner;

/** demand : Receive two integers from the user , And compare the output of the maximum of the two numbers */ public class TestMaxNum { public static void

main(String[] args) { //1. Prompt user for input System.out.println(" Please enter the first integer you want to compare :");

//2. Receive the integer input by the user , And give this value to the variable a To save int a = new Scanner(System.in).nextInt(); System.out

.println(" Please enter the second integer you want to compare :"); int b = new Scanner(System.in).nextInt();

//3. Compare two numbers received , Using ternary operators /**1 ? 2 : 3 * 1 It's an expression , if 1 The results are as follows true, The results are as follows 2 position , if 1 The results are as follows false, The results are as follows 3 position *

*/ //4. Defining variables max To save the maximum value of the comparison int max = a > b ? a : b; //5. Print maximum System.out.println(

" What is the maximum of the two numbers :"+max); /** Thinking questions : How to judge 3 Maximum number ? int max = a>b?(a>c?a:c):(b>c?b:c);*/ } }

<>1.5 practice ： Seeking the average year and leap year

create package : cn.tedu.basic

Create class : TestYear.java

demand : Year of receiving user input , Judge whether it is a normal year or a leap year package cn.tedu.basic; import java.util.Scanner; /** *

demand : Year of receiving user input , Judge whether it is a normal year or a leap year * If the year is a leap year , You need to meet one of the following two conditions : * condition 1: Can be 4 to be divisible by , And it can't be 100 to be divisible by *

condition 2: Can be 400 to be divisible by * */ public class Test3_Year { public static void main(String[] args

) { //1. Prompt and receive the year entered by the user System.out.println(" Please enter the year you want to judge :"); int year = new Scanner(

System.in).nextInt(); //2. Define a variable to hold the result String result = " Ordinary year ";// The default value is normal year , Suppose every year is an ordinary year

//3. Judge whether the year entered by the user meets the condition of leap year /** Solution 1*/ /** condition 1: Can be 4 to be divisible by , And it can't be 100 to be divisible by */ // if(year % 4 ==

0) {// Can be 4 to be divisible by // if(year %100 != 0) {// Can't be 100 to be divisible by // result =

" leap year ";// Meet the conditions of leap year 1, The result is a leap year // } // } // /** condition 2: Can be 400 to be divisible by */ // if(year % 400 == 0)

{// Can be 400 to be divisible by // result = " leap year ";// Meet the conditions of leap year 2, The result is a leap year // } /** Solution 2*/ /** Judgment structure

if( Judging conditions ){ The code to be executed after the judgment condition is met } */ //if( condition 1 || condition 2){ It's a leap year } //if(( Minor conditions 1 && Minor conditions 2) || condition 2){

It's a leap year } //if(( Can be 4 to be divisible by && Can't be 100 to be divisible by ) || Can be 400 to be divisible by ){ It's a leap year } if((year % 4 == 0 && year %100

!= 0) || year % 400 == 0){ result = " leap year ";// Meet the conditions of leap year , The result is a leap year } System.out.println(

year+" Year is "+result); } }

<>2 Expansion and supplement :

<>2.1 summary 1: Self increasing and self decreasing operators of arithmetic operators

a Is the operand ,++ Is the autoincrement operator ,– Is a self subtraction operator , Self increasing and self decreasing operators can be placed in front of variables , It can also be placed after variables , for example ：a++,++a,a–,--a etc .

Self increasing （++）： Add the value of the variable to the 1

Fractional prefix （ as ++a） And suffixes （ as a++）. The prefix is added first 1 Reuse ; Suffixes are used first and then added 1.

Self subtraction （–）： Subtracting the value of a variable 1

Fractional prefix （ as –a） And suffixes （ as a–）. The prefix is minus first 1 Reuse ; The suffix is used first and then subtracted 1.

<>2.2 summary 2: Logical operators

Logical operators connect two relational expressions or boolean variables , It is used to solve the combination judgment problem of multiple relational expressions

Note that the operation result returned by the logical operator is Boolean

usually , We use 0 express false, use 1 express true

And ： The relationship between expression and expression

& Shan Yu ： 1 & 2 , It turns out to be true, requirement 1 and 2 It has to be true

&& Double and ( Short circuit and )：1 && 2 , When 1 yes false Time ,2 It will be short circuited , Improve the efficiency of the program

or ： To express or relate to

| Single or ： 1 | 2, It turns out to be true, requirement 1 and 2 As long as there is one for you true Can

|| Double or ( Short circuit or )：1 || 2, When 1 yes true Time ,2 It will be short circuited , Improve program efficiency

<>2.3 summary 3: Priority control

When an expression contains more than one operator , You need to consider the priority of the operator , Operators with higher priority participate in the operation first , Operators with lower priority participate in the operation . In the actual development , There is no need to memorize the priority of operators , And don't deliberately use the precedence of operators , For unclear priority, use bracket to assist priority management .

Technology

- Java423 articles
- Python236 articles
- Vue127 articles
- Linux119 articles
- MySQL100 articles
- javascript76 articles
- SpringBoot72 articles
- C++68 articles
- more...

Daily Recommendation

views 4

views 3

©2019-2020 Toolsou All rights reserved,

Huawei 2021 session Hardware Engineer Logical post （FPGA） Super detailed surface !!!Vue-element-admin upgrade ui edition virtual machine VMware Download and install the most detailed tutorial !C++ Move constructor and copy constructor sound of dripping water java Backstage interview pygame Realize full screen mode and adjustable window size mysql Database setting character set configuration modification my.ini file （windows）30 What's the experience of being a junior programmer at the age of 20 C++ Multithreading programming （ Summary of common functions and parameters ）python_ cherry tree