Question

2. What are the three program control structures? Define each thoroughly and give an example of each.

3. Explain in detail the difference between a Class Variable and an Instance Variable. How do we declare a Class Variable?

4. Which of the following is true?
a.   Java programs can run on different platforms, like Windows and Unix, without being recompiled.
b.   C++ programs have always run more slowly than Java programs.
c.   In contrast to Java, C# requires programmers to manage almost all memory operations.
d.   All of the above.

Answer 1

2.Three program control structures are:

1.Conditional branches.

• This kind of control structure is used to select a path from the available two or more paths.
• It is further divided as if/else/else if, ternary operator, and switch.

Examples:

• if/else/if else:

If (c==2)

{

system.out.println(“ c is 2”);

}

else if (c==1)

{

System.out.println(“ c is 1”);

else

{

System.out.println(“ c is not 2 and 1”);

}

• Ternary operator:

System.out.println(a>b ? “a is greater than b”: “a is smaller or same as b”);

• Switch:

Int c=3;

switch(c)

{

case 0:

system.out.println(“ c is 1”);

break;

case 1:

System.out.println(“c is 2”);

break;

case 2:

System.out.println(“c is 3”);

break;

}

2.Loops

• This kind of control structure is used to iterate a specified number of instructions a particular number of times.
• It includes ‘while loop’, ‘For loop’, and ‘do-while’ loop.

Examples:

• while loop:

while (i>0)

{

System.out.println(“c is 3”);

}

• For loop:

for (i=0;i<n;i++)

{

System.out.println(“c is 2”);

}

• do-while loop:

do

{

System.out.println(“ c is 1”);

}while (i<n);

3.Branching statement:

• Branching statements are used to alter the flow of execution in loops.
• It includes ‘break’ and ‘continue’.

Examples:

• break:

We can exit early from a loop.

if(c==1)

{

System.out.println(“ c is 1”);

break;

}

• continue:

Skip the rest of the loop.

if(c==1)

{

Continue;

System.out.println(“c is 2 ”);

}

System.out.println(“c is 1”);

3.Differences:

• Class variables are declared with static keywords. An instance variable is declared with a 'new' keyword'.
• Class variables are created when the program starts. But instance variables are created when the object is created.
• Class variables can be assessed by calling its name along with the class name. But the instance variable can access directly by calling its name.
• In java, we declare the class variables as:

public class Varexamp

{

Int var;

static int data=10;

public static void main (String args[])

{

Varexamp obj = new Varexamp();

}

}

4.a.Java programs can run on different platforms, like Windows and Unix, without being recompiler.

• Java programs are “write once, run anywhere”.
• The java programs are once written can be run on any platform.
• Java is platform-independent.
• Java programs are slower than C++ programs. So option b is incorrect.
• C# does not require programmers to manage almost all memory operations. So option c is incorrect.
• So true statement is the option a.