java programming (junior programmer camp 7)

8/8/2019 Java Programming (Junior Programmer Camp 7)

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Java Programming

Junior Programmer Camp #7


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CHAPTER 1: BASICS OF JAVAJava Programming


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What is Java?

A high-level programming language

Useful for developing business applications

Java Development Kit download:http://www.oracle.com/technetwork/java/javase/downloads/index.html


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What is BlueJ?

A programming tool used for writing code in Java

Can be downloaded from bluej.org

Simple and easy to use for beginners


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Typical Java Code Skeleton

public class Program {

public static void main(String[] args) {

// your main code goes here

}

}


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Comments

Sometimes you may want to add some notes to yourJava code, without any effect to the code.

In this case, you can write comments.

Two ways:

System.out.println("test"); // print a test string

/*

This is a multiple-line comment.

More lineEven more line

Blah blah

*/


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Simple Program



System.out.println("Junior Programmer Camp 7");

}

}

OUTPUT:

Junior Programmer Camp 7


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Basic Arithmetics



System.out.println(1 + 2);

}

}

OUTPUT:

3


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Basic Arithmetics

Addition: 2 + 3

Subtraction: 4 5

Multiplication: 6 * 7

Division: 8 / 4

How about 2 + 3 * 4 ?


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Floating-Point Numbers

You can also use numbers with decimal points:2.3 1.5

Integers: , -3, -2, -1, 0, 1, 2, 3,

Real numbers: 0.0, 3.14, -2.4, 327.8

What is 3.0 / 4.0 in Java? 0.75

How about 3 / 4 ?


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Declaring and Using Variables

int x;

int y;

int z;

x = 2;

y = 5;z = x + y;

System.out.println(x + " + " + y + " = " + z);

OUTPUT:2 + 5 = 7


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Multiple Variable Declarations

Instead of

int x;

int y;

int z;

You can also use

int x, y, z;

to declare multiple variables all at once.


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Variable Initialization

Instead of

int x;

int y;

x = 2;y = 5;

You can also use

int x = 2, y = 5;

Try.


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Variable Types

Integers: byte, short, int, long

Floating-point numbers: float, double

Single character: char

Text: StringTrue/False: boolean


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Getting Inputs from the User

import java.util.Scanner;



Scanner sc = new Scanner(System.in);

int x = sc.nextInt();x = x * 2;

System.out.println(x);

}

}

INPUT: 1234

OUTPUT: 2468


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Multiple Inputs




Scanner sc = new Scanner(System.in);int x = sc.nextInt();

int y = sc.nextInt();

System.out.println(x);

System.out.println(y);

}

}

INPUT: 12

OUTPUT: 12


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Inputting Text




Scanner sc = new Scanner(System.in);

System.out.print("Enter your name: ");String name = sc.nextLine();

System.out.println("Hello, " + name + "!");

}

}

INPUT: John

OUTPUT: Hello, John!


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Quiz!

Write a program to get 2 numbers from the user and output the sum,the difference, and the product of those 2 numbers.

Hint: Follow the previous example.

INPUT: 73

OUTPUT: 10

4

21


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CHAPTER 2: CONTROL STRUCTURESJava Programming


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Introducing boolean Data Type

Normally you can use int to store integer numbers,

double to store floating-point numbers.

What if all you want is to store a truth value: either trueor false?

Answer: use boolean data type

Usage of this will be introduced later.


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To Do or not to Do?

Sometimes you will want your program to decidewhether to do something or not based on someconditions.

There are many ways to achieve this, for example:

if

switch


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General Form of if

if (condition) {

statements to do if condition is true

}


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If This Then Do That

if (1 == 2) {

System.out.println("1 is equal to 2");

}

if (1 != 2) {

System.out.println("1 is not equal to 2");}

OUTPUT: 1 is not equal to 2


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Do This or That

if (1 == 2) {

System.out.println("1 is equal to 2");

} else {

System.out.println("1 is not equal to 2");

}

OUTPUT: 1 is not equal to 2


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General Form of if-else

if (condition) {

statements to do if condition is true

} else {

statements to do if condition is false

}


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Do This or This, otherwise That

if (3 < 2) {

System.out.println("3 is less than 2");

} else if (3 > 2) {

System.out.println("3 is greater than 2");

} else {System.out.println("3 is equal to 2");

}

OUTPUT: 3 is greater than 2


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General Form of if-elseif-else

if (condition 1) {

statements to do if condition 1 is true

} else if (condition 2) {

statements to do if condition 2 is true

} else if (condition 3) {statements to do if condition 3 is true

} else {

statements to do if none of the conditions is true

}

// You can have as many conditions as you like!


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Using boolean Data Type

boolean check = (1 < 2);

if (check) {

System.out.println("1 < 2");

} else {

System.out.println("1 >= 2");}

/* Saw something?

The condition part of the if statement can be a boolean

expression (1 < 2) or a boolean variable (check)! */


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Condition with Multiple Cases

In some cases, you may need multipleconditionstatements to achieve your goals.

Writing them as multiple else-if statements can betedious.

Use of switch statement is recommended (with someexceptions).


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General Form of switch

switch (expression) {

// expression can be int, char, or boolean

case value1:

statements to do when expression == value1

break;case value2:

statements to do when expression == value2

break;

// add more cases as needed

default:

statements to do when nothing above matches

}


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Example Usage of switch// imported Scanner and instantiated one

System.out.print("Enter a number between 1 3: ");

int x = sc.nextInt();

switch (x) {

case 1:

System.out.println("Entered 1");

break;

case 2:

System.out.println("Entered 2");

break;

case 3:System.out.println("Entered 3");

break;

default:

System.out.println("Entered something else...");

}


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if-else Expression Shortcut

Instead of writing

int x = 0;

int y;

if (x == 0) {

y = 0;

} else {

y = x;

}

You can also use this:

int x = 0;

int y = x == 0 ? 0 : x;


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Quiz!

Write a program to get 3 numbers: x, y, and z. The program shouldoutput whether x + y = z or not. Can you do this with a switchstatement?

INPUT: 3

4

8

OUTPUT: 3 + 4 != 8


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CHAPTER 3: ITERATIONSJava Programming


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Iteration Fundamentals Sometimes you need to do certain things over and over again,

probably in the same or similar manner.

Writing 1000 Java statements to display numbers 1 to 1000 is notfeasible: you wouldn't want to try to copy-and-paste the codethousand times.

In this case, you can make use of the iteration feature of Javainstead.

There are 3 main ways to do this:

while do-while

for


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General Form of while

while (condition) {

statements to do while the condition is true

}


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1 - 1000

int i = 1;

while (i


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General Form of do-while

do {

statements to do, and to continue to do while the

condition is true

} while (condition);


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while and do-while differences

For the while loop, the conditionis checked before any statement isexecuted. Therefore, if the conditionis false in the first place, nostatement in the loop will be executed.

For the do-while loop, in contrast, the statements in the loop areexecuted once at first. Then, for each iteration, the condition ischecked in the same way as in the while loop.


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General Form of for

for (initialization; condition; iteration) {

statements to do as long as condition is true

}


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1 1000 using for

Use

for (int i = 1; i


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Quiz!

Write a game that let the player "guess" a random numbergenerated by the computer between 1 and 100. Each turn, displaywhether the input number is less than or greater than the randomone. Game ends when the player guesses correctly. Otherwise,keep asking for another number.

To random a number between 5 to 70: int x = (int) (Math.random() * (70 5 + 1) + 5);

Optional features:

The allowed min and max should change accordingly for eachturn. For example, if the random number is 40, and the userguesses 50, the game should now allow only numbers between1 and 49 in the next turn.

Game ends when there is only one number left to guess.


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CHAPTER 4: PROGRAMMING DRILLSJava Programming

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