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Flow control part 2 Iterative Method

                                                         Iterative Method

  • Iterative statement
    • while()
    • do-while()
    • for()
    • for-each()    1.5v
                                                            while()
If we don't know the number of iterations in advance then we should go for a while loop.
Example-:
/*
while(rs.next()){
}

while(e.hasmoreElements()){
}

while(itr.hasNext()){
}

*/

the argument should be the boolean type if we are trying to provide any other type then we will get compile time error.
syntax-:
  while(b){
        statements;
}

this syntax is applicable to c and C++  but this terminology is not allowed in Java.

while(1){
   System.out.print("hello");
}
compile time error-:
incompatible type error
found int type
required boolean.

curly-braces are optional and without curly braces, we can take only one statement under while which should not be a declarative statement.

Example-:
/*
while(true)                                                                
     statement;                                                                                                           
valid                                

while(true);
valid                                

 while(true)  
       int x=10;  
 invalid                                

while(true){
    int x=10;  
 }  valid

*/

/*
while(true){                                                                             
    System.out.pirnt("hello");                             
}                                                                                                                  
System.out.print("hi");                                                          
                                                                                                                          
compile time error                                                           
unreachable statement               
System.out.print("hi")               

while(false){ 
        System.out.print("hello");  
 } 
System.out.print("hi");      

compile time error 
 unreachable statement
 {

 int a=10,b=20;
 while(a<b){
   System.out.print("hello");
 }    
System.out.print("hi");

output "hello" infinite time




int a=10,b=20;                                                 
while(a>b){                                                                        
   System.out.print("Hello");                     
}                                                                                                         
System.out.print("Hi");                                

output-"Hi"                                                              
                                                      

  final int a=10,b=20; 
while(a<b){ 
       System.out.print("Hello"); 
 }         
System.out.print("Hi");  
compile time error   
unreachable statement         
                                                                                                                  
final int a=10,b=20;
while(a>b){
    System.out.print("Hello");
 }
System.out.print("Hi"); 
compile time error
unreachable statement
  {

*/

Note-: Every final variable will be replaced by a value at compile time only. 
                

Note -: If every argument is the final variable (compile time constant) then that operation should be performed at compile time only.


                                                do-while()
if we want executed loop body at least once then we should go for do while.
syntax-:
do{
    body;
}while(condition);

curly braces are optional and without curly braces, we can take only one statement b/w do and while which should not be a declarative statement.

/*
do{                                                                                                  
   statement;                                                  
}while(true);                                                 

valid                      

do;
   while(true); 
valid                        

do                
    int x=10;
while(true);
  
 NotValid  


do{                      
     int x=10;  
     }while(true);
 valid    


 do
    while(true);
NotValid


*/

spacial case

do while(true)
    System.out.print("hello");
while(false);
we can write this 
do
    while(true)
       System.out.print("Hello");
while(false);
is valid








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