Java: Flow of Control


If statement

The statement inside of an if must return a boolean value meaning true or false. (Note: C/C++ can return an integer). Otherwise, it is the same as in C/C++ (if, then, else if, else) Example:
if(count < 0)
 { System.out.println("Error!"); }
else if (count > 10)
 { System.out.println("Stop being a hog!");
   count = 0;  /*take that*/ }
else
 { System.out.println("Great Running!");
   count++; }



? operator

This conditional operator can also be used. This is the general formula:
test ? true_result_return : false_result_return
Here is an example:
int minimum = x < y ? x : y;



Switch

This is the same as in C/C++. Here is an example:
switch (option) {
   case 0:
      System.out.println("You choose Thresholding");
      Threshold();  /*call the treshold method of this class*/
      break;
   case 1:
      System.out.println("You choose Bit-Slicing");
      BitSlice();  /*call the Bit-slice method of this class*/
      break;
   default:
      System.out.println("Invalid Choice!");
      break;
}

//Threshold() and BitSlice() methods defined below



For loop

Same as in C/C++
Exercise


While loop

Same as in C/C++ except must have boolean test. Can break out of loops with break; statement and skip a loop with the continue; statements.
while (boolean test)
{ statements... }
Exercise


Do loop

Same as in C/C++ except must have boolean test. Can break out of loops with break; statement and skip a loop with the continue; statements.
do {
  statements.....
} while (boolean test)
 




Labeled Loops

  • break label;
  • continue label;
  • return expression;
  • label: statement;
Here is an example,
loop: while (true) {   //This is an infinite loop!
    switch(option = in.read()) {   //reads in a character
       case 0:
          Threshold(); //call treshold method
          break;
       case 1:
          BitSlice(); //call bitslice method
          break;
       default:
          System.out.println("Invalid Option!");
          break loop;  // jumps out of while-loop
    }
   
    System.out.println("Type in option choice");
}