JavaSE study notes - process control

Process control

1. Conditional flow control: if..else, switch
2. Loop flow control: while, do...while, for

Conditional flow control

if..else

grammar

   if(布尔表达式){
       //如果为true执行代码
   }[else if(布尔表达式){
       //....
   }]...
   [else{
       //...
   }]

Note
1. Boolean expressions in java can only be true/false
2. If there is only one curly brace in the execution body, it can be omitted
3. It is recommended to indent when writing if..else

switch

grammar

   switch(表达式){
       case 值1:[执行体;break;]
       ...
       case 值n:[执行体n;break;]
       [default:执行体;]
   }

Note
1. Expressions can only be byte/short/int/char/boolean, JDK5.0 extends enumeration types, JDK7.0 extends String.
Note: long type is not allowed
2. The judgment in the switch statement will only be executed Once, if the judgment is established, no further judgment will be made, usually with the break keyword to achieve the function

loop flow control

while,do…while，for

while loop

grammar

   while(布尔表达式){
       //循环体
   }

Note : Usually we need to provide loop end condition and step for loop control statement

do…while

grammar

  do{
      //执行体
  }while(布尔表达式);

for loop

grammar

   for(初始化表达式;布尔表达式;步进表达式){
       //循环体
   }

Note
1. The initialization expression is executed only once. Multiple variables of the same type can be initialized at the same time separated by commas
2. The core of the for loop is two colons. Always true if the boolean expression is omitted, and the step is 0 if the step expression is omitted

   for(;;){ //循环 } 等价于 while(true){//循环}

Loops can be nested

Features : If the number of executions is more, it will consume more time. In actual development, try to avoid the nesting of loops. Preferably no more than two levels of nesting.

   for(;;){ //外循环
       for(;;){ //内循环

       }
   }

Note : the change speed of the outer loop should be slow, and the change speed of the inner loop should be faster

• continue: means to end the current loop and execute the next loop.
• break: means to end the current entire loop
• Loops can be controlled using tags, using the tag syntax before the loop control statement: tagname: