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Java Fundamentals Cheat Sheet by

Find the basics of Java

Java Data Types

byte / short / int / long
-123, 10
float / double
235.13
char
'a', 'A', '$', '-'
boolean
true, false
String
'Alice', 'A234t'
 

Java Control Structures

If Statement
if ( expression ) {
­ statements
} else if ( expression ) {
­ statements
} else {
­ statements
}

While Loop
while ( expression ) {
­ statements
}

Do-While Loop
do {
­ statements
} while ( expression );

For Loop
for ( int i = 0; i < <va­lue­>; ++i) {
­ statements
}

For Each Loop
for ( var : collection ) {
­ statements
}

Switch Statement
switch ( expression ) {
­ case value:
­ ­ ­ statements
­ ­ ­ ­break;
­ case value2:
­ ­ ­ statements
­ ­ ­ ­break;
­ ­def­ault:
­ ­ ­ statements
}

Exception Handling
try {
­ ­sta­t­em­­ents;
} catch (Excep­t­i­onType e1) {
­ ­sta­t­em­­ents;
} catch (Exception e2) {
­ ­cat­c­h-all statem­­ents;
} finally {
­ ­sta­t­em­­ents;
}
 

Defining Methods

How to define any method in a class?
A class method can be declar­ed/­defined using the syntax: public­|pr­ivate [static] <re­tur­n_t­ype> <me­tho­d_n­ame­>([­arg­ume­nts])
How to call a static method?
Static methods are also called as class methods and they can be called directly without creating any instance.
How to call any instance method?
Instance or non-static method can only be called after instan­tiating the object. So first create an object from a class using <cl­ass­_na­me> <ob­j_n­ame> = new <cl­ass­_na­me>() and then call the method with this object. Ex.
Scanner scanner = new Scanne­r(S­yst­em.in);
int number = scanne­r.n­ext­Int();
 

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