Difference between revisions of "Java/C2/Nested-if/English"

Welcome

Learning Objectives

• Explain Nested-If Statements and Ternary operators.
• Use them in a Java program.

Tools Used

Ubuntu v 11.10,

JDK 1.6,and

Eclipse 3.7.0

Pre-requisites

- about the usage of relational and logical operators.

- if...else control flow statements.

If not, for relevant tutorial please visit our website which is as shown.

Nested-If statements

Syntax for Nested-If Statement

Point to the line of code as you explain.

if (condition1) {

if (condition2) {

Statement or block 1

}

else {

Statement or block 2

}

}

else {

Statement or block 3

}

In this case, if condition 1 is true, then the program checks for condition 2.

Condition 2 is given using another If statement.

If condition 2 is true, then the program executes Statement or block 1.

Else, it executes Statement or block 2.

If condition 1 is false, then the program will not check condition2.

Instead it will directly jump to its else statement i.e. block 3.

{ Minimize slides and open Eclise. It should contain the following }

public class NestedIfDemo {

public static void main(String args[]) {

}

}

We have created a class NesedIfDemo and added the main method to it.

int n = -5;

Highlight int n = -5;

 we will also handle negative numbers using a nested-if.

So inside the main method type

int n = minus 5;

We have created a variable n to store the negative number.

Now we shall write the if conditions.

if (n < 0) {

System.out.println(“Negative number”);

}

if (n < 0)

open curly bracket. Press enter

System.out.println Within brackets and double quotes (“Negative number”);

We first see if the number is a negative number.

If yes then we will not check for even and odd.

else{

}

else {

} Press enter

Now if the execution has come to the else part.

It means that the number is non negative.

So we check for odd or even inside this else part.

if (n % 2 == 0) {

System.out.println(“Even number”);

}

else {

System.out.println(“Odd number”);

}

if (n modules 2 double equal to 0) { Press enter

System.out.println(“Even number”);

}

else {

System.out.println(“Odd number”);

}

So we make sure that negative numbers are not considered for odd or even check.

now Let us try a positive number

Save and Run the file

Now Save and run the file

There is no limit to the amount of nesting.

But it is a good practice to not go beyond 3 levels of nesting.

First let me clean up the Main method.

It is a very trivial program but the issue comes in dividing odd numbers.

When 7 is divided by 2, we get 3.

But what if we want the result to be rounded off.

Which means, when 7 is divided by 2, we get 4 and not 3

In simple terms, we need the next number.

int n, nHalf;

int n, nHalf;

We will store the number in n and the half number in nHalf

n = 5;

if (n % 2 == 0) {

nHalf = n / 2;

}

else {

nHalf = (n + 1) / 2;

}

n = 5;

if (n % 2 == 0) { Press enter

nHalf = n / 2;

}

else {

nHalf = (n + 1) / 2;

}

We check if the number is even or odd and do the division accordingly.

System.out.println(nHalf);

So  Type

System.out.println(nHalf);

Point to the output.

As we can see, our objective is met. We get the output as 3 and not 2

There is more syntax than logic in our program.

This is when ternary operator makes code simpler.

Slide 7

Ternary Operator.

It Provides a short syntax and is denoted by a question mark.

It Takes three operands at a time.

Point to the syntax

Syntax of Ternary Operator

Syntax:

Result = Expression ? Operand 1 : Operand 2

The expression is the condition that has to be checked.

Operand 1 is the value of the variable Result if the condition is true.

Operand 2 is the value if the condition is false.

Now Let us use it in our program.

Remove the if-else statement

nHalf = n % 2 == 0 ? n / 2 : (n + 1) / 2

nHalf = n % 2 == 0 ? n / 2 : (n + 1) / 2 semi-colon

This statement reads,

if n is even, nHalf is n by 2.

Otherwise, it is n plus 1 by 2.

Save and Runthe file. Press Ctrl S and Ctrl F11 keys

This way, ternary operator reduces clutter in the code and improves readability.

Summary

In this tutorial we have learnt:

• About Nested-If Statements and Ternary Operator
• Usage of Nested-If Statements and Ternary Operator in a Java program

Assignment

Nested-If and Ternary operator. Write java program for the following.

• Check whether a number is even and also a multiple of 11 using nested-if.
• Identify the largest number among the two given numbers using Ternary operator.

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