Process control statement

Flow control statement

 Summary of knowledge points : Flow control statement 
 One . if...else  Statements can be seen as having 4 In the form of ：
1)  if sentence 
if( Boolean expression ){  If the Boolean expression is true Statement to be executed }
2) if...else  sentence 
if( Boolean expression ){  If the value of a Boolean expression is true} else{ If the value of a Boolean expression is false}
3) if...else if...else sentence 
 Format :    if( Boolean expression 1){ If the Boolean expression 1 The value of is true Execute code }
else if( Boolean expression 2){  If the Boolean expression 2 The value of is true Execute code }
else if( Boolean expression 3){ If the Boolean expression 3 The value of is true Execute code }
else { If none of the above Boolean expressions are true Execute code }

 Two . Nested  if…else  sentence 
 Format :   if( Boolean expression 1){ If the Boolean expression 1 The value of is true Execute code 
if( Boolean expression 2){ If the Boolean expression 2 The value of is true Execute code }}

 3、 ... and .switch sentence 
switch case  Sentences have the following rules ：
1)switch  The variable type in a statement can be ： byte、short、int perhaps  char、enum. from  Java SE 7  Start ,
switch  Support string  String  Type , meanwhile  case  Label must be a string constant or literal .
2)switch  Statements can have more than one  case  sentence . Every  case  Followed by a value and colon to compare .
3)case  The data type of the value in the statement must be the same as the data type of the variable , And it can only be a constant or literal constant .
4) When the value of a variable is equal to  case  When the values of the statements are equal , that  case  Statement after statement begins execution , until  break  The sentence will jump out  switch  sentence .
5) When you meet  break  When the sentence is ,switch  Statement termination . The program jumps to  switch  Statement execution after statement .case  The statement does not have to contain  break  sentence . without  break  The statement appears , The program will continue with the next  case  sentence , Until it appears break  sentence .
6)switch  A statement can contain a  default  Branch , This branch is usually  switch  The last branch of the statement （ Can be anywhere , But usually in the last ）.default  In the absence of  case  Execute when the value of a statement is equal to the value of a variable .default  Branches don't need  break  sentence .  switch( expression ) {
case Expression value 1: Sentence block 1;
break; 
case expression N： Sentence block N;
break;default： Sentence block ;}