Lecture 3

Lecture Topic:

Flow of control (For loop, Do-while loop, Continue, Break)
Data type and corresponding class
Packages
Visibility
Objects and Classes

For Loop

Syntax:

for (init; test; statement) { statements; }
NULL statement:

for (int i =0; i &lt= 99; i++) { }
Inifinite Loop:

for ( ; ; ) { if (?) break; }
Compound Condition:

for (i=0, j=10; i <100; i++, j+=2)
", " is permitted in increment initialization part of body of FOR loop.

Do-While Loop

Like "repeat-until" loop, loop will execute at least once.

Syntax:

do {
statements;
} while (expression)

Continue

-- Abort out of the iteration.

Syntax:

continue; // break out the current loop
continue identifier; // goto the labeled outer loop

Example:

foo : for (int i =1; i <10; i++) { for ( int j=1; j <10; j++) { if (i%J==2) continue foo; // break to the outer loop system.out.print(i * j + " "); } }

Break

Syntax:

break; // jumps to outside of the nearest loop
break identifier; // break to outside of the labeled nested loop

Example:

overbudget = false; SS: for (i = 0; i <10; i++) { for (j=0; j <10; j++) { if (coust[i+j] >10) { overbudget = true; break SS; // break out of {SS: for(;;)} } } } if (overbudget) system.out.println("Ran out of money"); else system.out.println("Spend More ! ");

Data types and their corresponding class

Basic Type Corresponding Class boolean Boolean char Character int Integer long Long float Float double Double
Example:

Integer foo = new Integer(10); // integer object foo =10 int i = 3; // integer variable = 3

Packages

         packages == like a library in C/C++.



         Syntax:


              import package  typically;



import package classname;

import package * ;



Note:  Extra imports are discarded,  no extra linked code added.

Visibility

-- is field modifier in class

Type:
  public -- world accessible protected -- class / subclass / package
default -- package access private protected -- class / subclass access private
-- accessible only within class 
  
Example: package graphics; public class circle
// add class circle to library { public int x, y; //(1) world access properties
or private protected x, y; //(2) class and subclass access void move(int
x1, y1) { x=x1; y=y1;} } package fruits; public class apple { int i; } //
adding apple class to library package fruits; public class plums { int y;
} // adding apple class to library package Sauce; import package fruits
*; // include another library public class chestnut { } ; // adding apple
class to library

Objects and Classes

--Objects have types




   apple mash (apple a)               // return type Class apple

        {   a.c =0;   return  1;  }



   class Point {                     // Class of Point

           public double x, y;       // data member of Point of class

          }

   Point  p1 = new Point();         // create object of Point

      p1.x = 10;                         // assign value to x

      p1.y = 11;                         // assign value to y