JAVA LESSON-02.pptx

Java Programming
CONDITIONAL STATEMENT, JAVA LOOPING, AND JAVA ARRAY

Java Switch
 The switch expression is evaluated once.
 The value of the expression is compared with the values of each case.
 If there is a match, the associated block of code is executed.
 The break and default keywords are optional, and will be described later in
this chapter

Java Switch
Syntax:
int day = 4;
switch (day) {
case 1:
System.out.println("Monday");
break;
case 2:
System.out.println("Tuesday");
break;
case 3:
System.out.println("Wednesday");
break;
case 4:
System.out.println("Thursday");
break;
case 5:
System.out.println("Friday");
break;
case 6:
System.out.println("Saturday");
break;
case 7:
System.out.println("Sunday");
break;
}
switch(expression) {
case x:
// code block
break;
case y:
// code block
break;
default:
// code block
}

Java Switch
The break Keyword
When Java reaches a break keyword, it breaks out of the switch block.
This will stop the execution of more code and case testing inside the block.
When a match is found, and the job is done, it's time for a break. There is no need
for more testing.
The default Keyword
The default keyword specifies some code to run if there is no case match.

Java Loop
Loops
Loops can execute a block of code as long as a specified condition is
reached.
Loops are handy because they save time, reduce errors, and they make
code more readable.
3 types of Loop in Java
 While Loop
 Do/While Loop
 For Loop

Java While Loop
The while loop loops through a block of code as long as a specified condition is true:
while (condition) {
// code block to be executed
}
int i = 0;
while (i < 5) {
System.out.println(i);
i++;
}

Java Do/While Loop
The do/while loop is a variant of the while loop. This loop will execute the code block
once, before checking if the condition is true, then it will repeat the loop as long as the
condition is true.
do {
}
while (condition);
int i = 0;
do {
i++;
}
while (i < 5);

Java For Loop
When you know exactly how many times you want to loop through a block of code,
use the for loop instead of a while loop.
 Statement 1 is executed (one time) before the execution of the code block.
 Statement 2 defines the condition for executing the code block.
 Statement 3 is executed (every time) after the code block has been executed.
The example below will print the numbers 0 to 4:
for (statement 1; statement 2; statement 3) {
}
for (int i = 0; i < 5; i++) {
}

Java Array
Arrays are used to store multiple values in a single variable, instead of declaring
separate variables for each value.
To declare an array, define the variable type with square brackets:
We have now declared a variable that holds an array of strings. To insert values to it, we
can use an array literal - place the values in a comma-separated list, inside curly braces:
To create an array of integers, you could write:
String[] cars;
String[] cars = {"Volvo", "BMW", "Ford", "Mazda"};
int[] myNum = {10, 20, 30, 40};

Java Array
Access the Elements of an Array
You access an array element by referring to the index number. This statement accesses
the value of the first element in cars:
Note: Array indexes start with 0: [0] is the first element. [1] is the second element, etc.
System.out.println(cars[0]);
// Outputs Volvo

Java Array
Change an Array Element
To change the value of a specific element, refer to the index number:
cars[0] = "Opel"
System.out.println(cars[0]);
// Outputs Opel instead of Volvo

Java Array
Array Length
To find out how many elements an array has, use the length property:
Loop Through an Array
You can loop through the array elements with the for loop, and use the length
property to specify how many times the loop should run.
The following example outputs all elements in the cars array:
String[] cars = {"Volvo", "BMW","Ford","Mazda"};
System.out.println(cars.length)
;// Outputs 4
for (int i = 0; i < cars.length; i++) {
System.out.println(cars[i]);
}

JAVA USER INPUT
Scanner
The Scanner class is used to get user input, and it is found in the java.util
package.
To use the Scanner class, create an object of the class and use any of the
available methods found in the Scanner class documentation. In our example,
we will use the nextLine() method, which is used to read Strings:

JAVA USER INPUT
import java.util.Scanner; // Import the Scanner class
class MyClass {
public static void main(String[] args) {
Scanner input = new Scanner(System.in); // Create a Scanner object
System.out.println("Enter username");
String userName = input.nextLine(); // Read user input
System.out.println("Username is: " + userName); // Output user input
}
}

JAVA USER INPUT
Method Description
nextBoolean() Reads a boolean value from the user
nextByte() Reads a byte value from the user
nextDouble() Reads a double value from the user
nextFloat() Reads a float value from the user
nextInt() Reads a int value from the user
nextLine() Reads a String value from the user
nextLong() Reads a long value from the user
nextShort() Reads a short value from the user

JAVA LESSON-02.pptx

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