Multi branch structure

1、 Multiple branches
-else if
-switch

2、else if grammar
if( expression ){
sentence 1
}else if( expression 2){
sentence 2
}else{
sentence 3
}

3、switch grammar
switch( Conditional expression ){
case value 1: Code 1;break;
case value 2: Code 2;break;
case value 3: Code 3;break;
…
default: Code n
7j}