1 if statement

1.1 syntax

if(expression)
{
Execute action
}

1.2 Complex logic

Associative operator precedence writing condition:

• Highest priority: ()
• Lowest priority:=
• Priority: !>Arithmetic Operators>Relational Operators>&& >||
  Note: Use parentheses for complex conditions to improve readability

1.3 Multiple if

• Syntax: if----else if --else
• if can only be in the first place, and there must be one
• else, only at the last and at most one
• else if in the middle, there can be several (0-n)
• if-else-if-else: It is judged from top to bottom, and the first result is true, execute the code, after the code block is executed, jump out

1.4 Nested if selection structure

• In order to make the code more readable, higher and more logical
• In a single code block, it is best not to exceed three levels of nesting at a time. If it exceeds, check the logic

2 swith statement

• The condition is not a boolean type, except for long unexpected integer + enumeration + string+char after jdk (1.7)
• The swtich comparison must be the equivalent judgment of the constant and the constant cannot be repeated
• break, prevent penetration
• switch is a separate scope
• switch does not need a comparison, finds the target at one time 6. defautl, when all conditions are not satisfied, execute default; it may or may not be
• can be in any position, but usually, we habitually put it at the first or at the end; if it is not at the end, we usually add break.

3 loops

3.1 while loop

3.1.1 Syntax

while(loop condition)
{
Execute action
}

3.1.2 The Four Steps of the Cycle

• Initial Conditions: Where to Start
• Judging conditions, where does it end
• The body of the loop is the main content of the loop execution
• Iteration: infinite approach to the goal

3.1.3 The difference between while and do-while loops

• When the condition is not met, do not execute it once; first judge that it is executing
• When the do-while loop, when the conditions are met, execute at least once; execute first, then judge
• Loops have fixed and variable lengths
• Order and Flashback
• Define step size
• Multiple criteria
  

3.2 for loop

3.2.1 Syntax

for(parameter initialization; conditional judgment; update loop variable)
{
Execute operation
}
For example: For( ; ; ){}

3.3 Jump and Skip

3.3.1 Syntax

Break //Jump out of all loops (only valid for the current loop)
Continue //Skip this loop (only valid for the current loop)

3.4 Flowchart