Java (3) if structure

first, basic if structure

1. Flowchart

1) Input/output

2) Judging and branching

3) Process Line

　　1.1 Simple if condition to judge

if ( expression ) {

the // expression is true to execute the code in {}

}

Example 1 : If Zhang San's java score is greater than 98, then the teacher rewards him with a MP4. 　　

1  Public classPractice1 {2      Public Static voidMain (string[] args) {3                 //enter Zhang San's score from the console4Scanner input =NewScanner (system.in);5System.out.print ("Please enter the Java score for Zhang San:");6         intScore =input.nextint ();7         if(Score >98){8SYSTEM.OUT.PRINTLN ("Teacher said: Yes, rewarding a mp4! ");9         }Ten     } One}

If Structure

Run the results,

1) Realization of the conditions of operation results

2) operating results without conditions

　　1.2 Simple if condition to judge

if ( expression ) {

// expression is true , execute here

}else{

// expression is false , this line here

}

Example 2　　 : If Zhang San's java score is greater than 98, then the teacher rewards him with a MP4, otherwise the teacher punishes him to copy the test paper.　

1  Public classPractice2 {2      Public Static voidMain (string[] args) {3Scanner input =NewScanner (system.in);4System.out.print ("Please enter the Java score for Zhang San:");5         intScore =input.nextint ();6         if(Score >98){7SYSTEM.OUT.PRINTLN ("Teacher said: Yes, rewarding a mp4! ");8}Else{9System.out.println ("The teacher said:" A copy of the paper));Ten         } One     } A}

If-else Structure

Run the results,

1) Realization of the conditions of operation results

2) Implementation of the conditions are not set up the results of the operation

Description: If the If or else is followed by, and there is only one line of code, {} can be omitted, but it is not recommended to omit

second, logical operators

A. && Logic and (press shift+7)--and (and, at the same time)

Multiple conditions, 1 are false, if () all false, multiple conditions are true at the same time, if () is true

B. | | (Press shift+ to enter the above |) --or (or) multiple conditions, as long as 1 are true, if () all are true

C. ! (in English state)--Take the inverse example: Not equal to! =

1) Determine if the strings are equal

A , case-sensitive: password

String Variables . Equals ( the value of a string or a string variable )

B , Case insensitive: Verification Code

String Variables . Equalsignorecase ( value of string or string variable )

2) How to break down numbers on single, 10, Hundred, thousand? "P47"

Int digit = number% 10//decomposition get single digit

Int 10 bit = number/10 10//decomposition get 10 digits

Int hundred = number/100% 10//decomposition to get the number of hundred

INT thousand = number/1000% 10//Decomposition get thousand

third, multiple if structure

if ( condition 1) {

// code block

}else if ( condition 2) {

// code block

}else if ( condition N) {

// code block

} else{

// code block

}

Example 3: Xiao Ming's classmates took part in the course of Java study, her parents admit Connaught:

1) If the test result equals 100 points, the father buys a car for her

2) If the test scores >=90, the mother buys her a laptop computer

3) If the test scores >=60, mother buys her a cell phone

4) If the test results <60 points, deduct one weeks of living expenses

1  Public classPractice3 {2      Public Static voidMain (string[] args) {3Scanner input =NewScanner (system.in);4System.out.println ("Please enter score:");5         intScore=input.nextint ();6         if(score== 100){7System.out.println ("Father buys her a car");8}Else if(score>= 90){9System.out.println ("Mother buys a laptop for her");Ten}Else if(score>=60){ OneSystem.out.println ("mother buys her a cell phone"); A}Else{ -System.out.println ("One weeks of living expenses deducted"); -         } the     } -}

multiple if selection structure

Run the results (sequentially):

　　

　　

　　

　　

Description: An else if can have multiple, sequential requirements on the number range

Enter String--if in if (variable name. Equals ("string")) {}

Iv. Nested IF Structures

if ( condition 1) {

                   // code block

I f ( condition 1-1) {

}

Description: The if structure can be a if , If...else , multiple if and other structures

} else{

can be for if , If...else , multiple if and other structures

}

Example 4: The School holds a sports meeting, the students in the hundred-meter race in 10 seconds are eligible to enter the final, according to the gender division of the men's and women's groups.

1  Public classPractice4 {2      Public Static voidMain (string[] args) {3Scanner input =NewScanner (system.in);4System.out.print ("Please enter the match score (s):");5         DoubleScore =input.nextdouble ();6System.out.print ("Please enter gender");7String gender =Input.next ();8         if(score<=10){9             if(Gender.equals ("Male")){TenSystem.out.println ("Enter the men's team finals"); One}Else if(Gender.equals ("female")){ ASystem.out.println ("Enter the women's team finals"); -             } -}Else{ theSystem.out.println ("obsolete"); -         } -     } -}

Nested IF Structures

Run the results,

1.2.

3.4.

5.6.

Description: 1. The condition of the inner if is only judged if the condition of the outer if selection structure is satisfied

2.else is always paired with the missing else if

Note:The writing specification for the IF structure:

　　　　--to make the if structure clearer, enclose the block of code that each if or else contains in curly braces.

--matched pairs of if and else should be left justified

-The IF structure of the inner layer must be indented relative to the outer if structure

Java (3) if structure