Java Basics (3)

First, basic if structure

1. Flowchart

Input/Output

Judging and branching

Process Line

1.1 Simple if condition to judge

if ( expression ) {

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

}

1.2 Simple if condition to judge

if ( expression ) {

                   // expression is true , execute here

}else{

                   // expression is false , this line here

}

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

L && 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

L | | (Press shift+ to enter the above |) -or (OR)

Multiple conditions, as long as 1 are true, if () all is true

! (in English state)--take the inverse not equal to! =

L determine if 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 )

How do I break down numbers in bits, 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}

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

in the if input string--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 an if, if...else, multiple if structure} else{can be if, if...else, multiple if and other structures}

V. Syntax for switch structure (switching statements)

5.1 Switch structure use:

int \char 2 Types of equivalence judgment to use

5.2. Switch structure and if structure similarities and differences

Same point: equal judgment can be achieved

Different points:

1. Different syntax

2. The use of different occasions

3. If structure, focusing on range judgment

4. Switch structure, focusing on equivalence judgment, type can only be int, char type

5. Efficiency:

In the equivalence judgment, the switch structure efficiency is higher than the IF structure

Vi. exception handling--hasnextint ();

Determines whether an integer

if (Input.hasnextint ()) {//Boolean type

code block

}

Java Basics (3)