Learn Scala if Else statement

scala It's a multi paradigm （multi-paradigm） Programming language , The original intention of the design is to integrate various features of object-oriented programming and functional programming .Scala Running on the Java Virtual machine , And compatible with existing Java Program .

Scala IF...ELSE Statement is the result of execution through one or more statements （True perhaps False） To determine the code block to execute .
You can simply understand the execution process of conditional statements through the following figure :

if Statements are composed of Boolean expressions and subsequent statement blocks .

if The syntax format of the statement is as follows ：

if( Boolean expression )
{
   //  If the Boolean expression is  true  The statement block is executed 
}

If the Boolean expression is true Then execute the statement block in the braces , Otherwise, the statement block in the bracket will be skipped , Execute the statement block after the braces .

object Test {
   def main(args: Array[String]) {
      var x = 10;

      if( x < 20 ){
         println("x < 20");
      }
   }
}

Execute the above code , The output is ：

$ scalac Test.scala 
$ scala Test
x < 20

if After the statement, you can follow else sentence ,else The statement block within can be in the Boolean expression as false When it comes to execution .

if...else The syntax of is as follows ：

if( Boolean expression ){
   //  If the Boolean expression is  true  The statement block is executed 
}else{
   //  If the Boolean expression is  false  The statement block is executed 
}

object Test {
   def main(args: Array[String]) {
      var x = 30;

      if( x < 20 ){
         println("x  Less than  20");
      }else{
         println("x  Greater than  20");
      }
   }
}

Execute the above code , The output is ：

$ scalac Test.scala 
$ scala Test
x  Greater than  20

if After the statement, you can follow else if...else sentence , It is useful in the case of multiple conditional statements .

if...else if...else The syntax is as follows ：

if( Boolean expression  1){
   //  If the Boolean expression  1  by  true  The statement block is executed 
}else if( Boolean expression  2){
   //  If the Boolean expression  2  by  true  The statement block is executed 
}else if( Boolean expression  3){
   //  If the Boolean expression  3  by  true  The statement block is executed 
}else {
   //  If all of the above conditions are  false  Execute the statement block 
}

object Test {
   def main(args: Array[String]) {
      var x = 30;

      if( x == 10 ){
         println("X  The value of is  10");
      }else if( x == 20 ){
         println("X  The value of is  20");
      }else if( x == 30 ){
         println("X  The value of is  30");
      }else{
         println(" Unable to judge  X  Value ");
      }
   }
}

Execute the above code , The output is ：

$ scalac Test.scala 
$ scala Test
X  The value of is  30

if...else Nested statements can be implemented in if One or more statements are embedded in if sentence .

if...else The syntax format of nested statements is as follows ：

if( Boolean expression  1){
   //  If the Boolean expression  1  by  true  The statement block is executed 
   if( Boolean expression  2){
      //  If the Boolean expression  2  by  true  The statement block is executed 
   }
}

else if...else Nested statements similar if...else Nested statement .

object Test {
   def main(args: Array[String]) {
        var x = 30;
        var y = 10;

         if( x == 30 ){
            if( y == 10 ){
            println("X = 30 , Y = 10");
         }
      }
   }
}

Execute the above code , The output is ：

$ scalac Test.scala 
$ scala Test
X = 30 , Y = 10

This paper addresses ：https://www.linuxprobe.com/learn-scala-if.html