Java full tutorial video in english language|Learn everythings from java|Programmingwithmosh

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e smallest building blocks in Java programs are methods (also called functions
in other programming languages). We combine related methods in classes, and
related classes in packages. This modularity in Java allows us to break down large
programs into smaller building blocks that are easier to understand and re-use.
5 Interesting Facts about Java
1. Java was developed by James Gosling in 1995 at Sun Microsystems (later
acquired by Oracle).
2. It was initially called Oak. Later it was renamed to Green and was finally
renamed to Java inspired by Java coffee.
3. Java has close to 9 million developers worldwide.
4. About 3 billion mobile phones run Java, as well as 125 million TV sets and
every Blu-Ray player.
5. According to indeed.com, the average salary of a Java developer is just over
$100,000 per year in the US.
Types
Variables
We use variables to temporarily store data in computer’s memory. In Java, the type
of a variable should be specified at the time of declaration.
In Java, we have two categories of types:
• Primitives: for storing simple values like numbers, strings and booleans.
• Reference Types: for storing complex objects like email messages.
Primitive Types
Declaring Variables
byte age = 30;
long viewsCount = 3_123_456L;
float price = 10.99F;
char letter = ‘A’;
boolean isEligible = true;
• In Java, we terminate statements with a semicolon.
Type Bytes Range
byte 1 [-128, 127]
short 2 [-32K, 32K]
int 4 [-2B, 2B]
long 8
float 4
double 8
char 2 A, B, C, …
boolean 1 true / false
• We enclose characters with single quotes and strings (series of characters) with
double quotes.
• The default integer type in Java is int. To represent a long value, we should add L
to it as a postfix.
• The default floating-point type in Java is double. To represent a float, we should
append F to it as a postfix.
Comments
We use comments to add notes to our code.
// This is a comment and it won’t get executed.
Reference Types
In Java we have 8 primitive types. All the other types are reference types. These
types don’t store the actual objects in memory. They store the reference (or the
address of) an object in memory.
To use reference types, we need to allocate memory using the new operator. The
memory gets automatically released when no longer used.
Date now = new Date();
Strings
Strings are reference types but we don’t need to use the new operator to allocate
memory to them. We can declare string variables like the primitives since we use
them a lot.
String name = “Mosh”;
Useful String Methods
The String class in Java provides a number of useful methods:
• startsWith(“a”)
• endsWith(“a”)
• length()
• indexOf(“a”)
• replace(“a”, “b”)
• toUpperCase()
• toLowerCase()
Strings are immutable, which means once we initialize them, their value cannot be
changed. All methods that modify a string (like toUpperCase) return a new string
object. The original string remains unaffected.
Escape Sequences
If you need to use a backslash or a double quotation mark in a string, you need to
prefix it with a backslash. This is called escaping.
Common escape sequences:
• \\
• \”
• \n (new line)
• \t (tab)