Control syntax operator

Typical control syntax

"Sequential, branch, repeat"
Any complex program can be created with the above three combinations! 　

* if statement *

If the conditional expression is matched, execute the process ##### * Basic syntax * 
if(Conditional expression) {
Processing when the conditional expression is matched;
   }else  
Processing when the conditional expression does not match;
}

* while statement *

Repeat the process while the conditional expression is matched ##### * Basic syntax * ``` while(Conditional expression) { Repeated processing when the conditional expression is matched; } ``` ##### * do while statement * ``` do{ Repeated processing }while(Conditional expression); 
 <strong> The process is executed at least once </ strong> because it is evaluated by the conditional expression after it is executed. This is called <strong> post-judgment </ strong> (↔︎ pre-judgment) </ dd>

### * for statement *
 <dd> <strong> Specify the number of repetitions and repeat the process </ strong> </ dd>
##### * Basic structure of for statement *

for (① int variable name=initial value;② Variable name<Number of repetitions;③ Repeated processing) { Repeated processing }

 <dd> (1) Substitute a variable to record the number of laps of the loop. <Strong> Loop variable </ strong> </ dd>
 <dd> ② Conditional expression to determine whether to continue the loop </ dd>
 <dd> ③ Process executed after the repeated process is completed (after reaching "}") </ dd>

##### * About loop variables *
 <dd> ・ Can be used for calculation and display in blocks </ dd>
 <dd> ・ Cannot be used outside the for statement </ dd>

##### * Interruption of iterative processing *
 <dd> ・ <strong> break statement </ strong> and <strong> continue statement </ strong> can interrupt the iterative process </ dd>
 <dd> Basic syntax of break statement (example: when processing is interrupted at the 5th time) </ dd>

for (int i = 1; i < 10; i++) { if(i==5){ break; 　} Repeated processing }

 <dd> Basic syntax of continue statement (example: when processing only the 5th time) </ dd>

for (int i = 1; i < 10; i++) { if(i==5){ continue; 　} Repeated processing }



### * switch statement *
 <dd> <strong> If there are multiple judgment conditions, it can be described completely from if <strong> </ dd>
##### * Terms of use for switch statements *
 <dd> ・ It must be a condition to compare whether the left and right match. </ Dd>
 <dd> -The value to be compared is not a decimal or boolean value </ dd>

##### * Basic syntax of switch statement *

switch(Variable name) { case value 1: Processing when the variable matches the value 1 break; /*End the process with break case value 2: Processing when the variable matches the value 2 break; default : Processing when variables do not match all values }


## Control syntax components
 ʻIf (conditional expression) {`
 <strong> block </ strong>
　`}`  

#### * Characteristics of conditional expressions *
 <dd> -The conditional expression must have an evaluation result of `true` or` false` </ dd>

#### * When using a character string in a conditional expression ... *
 <dd> ・ `.equals ("string ")` </ dd> instead of `= ("string ")`

#### * Block features *
 <dd> -Variables declared within a block are valid only within the declared block </ dd>
 <dd> -The range of places where variables can be used is called ** scope ** </ dd>

## Relational operator
 <dd> Symbols used in conditional expressions </ dd>
 |operator|meaning| 
 |:-----------|--------:|
 | ==         |Left side and right side are equal|
 | !=         |The left side and the right side are different|
 | >          |Left side is less than right side|
 | <          |The left side is more than the right side|
 | >=         |The left side is more than the right side|
 | <=         |The left side is below the right side|


## Logical operator
 |operator|meaning| 
 |:----------|--------:|
 |&&         |AND|
 |ll       |OR (or)|

## Negation operator
 <dd> ・ Before the conditional expression! By adding, the value of the conditional expression, true / false, can be reversed. </ Dd>
###### ʻIf (! (name.equals ("a"))) `→ name = a <strong> unless </ strong>