| Variables | |
type variable = value;
| Dynamic variable definition, for example int a=2; double x, y; |
type static variable
| Static variable definition (fix memory location) |
byte
short
int
long
float
double
boolean
String (or any object)
char
| Formats |
type[] variable;
| Array definition, for example int[] anArray; String[] buffer = new String[10]; |
anArray = new int[10];
anArray[0] = 100;
| Value assignment |
int[] anArray = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10};
String[][] names = {{"Mr. ", "Mrs. ", "Ms. "},{"Smith", "Jones"}};
| Array value assignment |
byte[] anArray;
short[] anArray;
long[] anArray;
float[] anArray;
double[] anArray;
boolean[] anArray;
char[] anArray;
String[] anArray;
| Other type of array definitions |
java.awt.Color.red
java.awt.Color.white
java.awt.Color.blue
| Color |
java.text.NumberFormat formatter = new java.text.DecimalFormat("0.0E00");
stext = formatter.format(fvalue);
| Format |
| Operators | |
expr++
| expr=expr + 1 |
expr--
| expr=expr - 1 |
++expr
| |
--expr
| |
+expr
| |
-expr
| |
* / %
| Multiplicative |
+ -
| Additive |
== !=
| Equality |
>
| Greater than |
>=
| Greater than or equal to |
<
| Less than |
<=
| Less than or equal to |
<<
| Signed left shift |
>>
| Signed right shift |
>>>
| Unsigned right shift |
< > <= >=
| instanceof relational |
~
| Unary bitwise complement |
&
| Bitwise AND |
^
| Bitwise exclusive OR |
|
| Bitwise inclusive OR |
&&
| Logical AND |
||
| Logical OR |
?:
| Ternary |
=
| |
+=
| |
-=
| |
*=
| |
/=
| |
%=
| |
&=
| |
^=
| |
|=
| |
<<=
| |
>>=
| |
>>>=
| Assignment |
instanceof
| Compares an object to a specified type |
static double variable
| Variables that are common to all objects |
static final double PI = 3.141592653589793;
| Constants |
Enum Types
public enum Day {
SUNDAY, MONDAY, TUESDAY, WEDNESDAY,
THURSDAY, FRIDAY, SATURDAY
}
| Arrays of fix values |
| Functions | |
public type function( arguments ) {}
| Public function |
privat type function( arguments ) {}
| Privat function |
public void function() {}
|
public int function() {}
|
public double function(int a, double b) {}
| Examples of functions |
public static void main(String[] args) {}
| Function with an array argument |
| Control Flow Statements | |
if (condition) statement1;
| if-then, for example if(a>0){ n = 1; } |
if (condition) { statement1; }
else { statement2; }
| if-then-else, for example if(a>0){ n = 1; }else{ n = 0; } |
if (condition) { statement1; }
else if { statement2; }
else { statement3; }
| if-then-else if-then-else |
switch (variable) {
case 1: statement1; break;
case 2:
case 3: statement2; break;
default: statement3; break;
}
| Switch Statement |
while (expression) {
statement(s)
}
| While Statements |
do {
statement(s)
} while (expression)
| Do-while Statements |
for (initialization; termination; increment) {
statement(s)
}
| for Statement |
for/while-do loop {
if (conditions) { break; }
}
| Break Statement (unlabeled break) |
label: statement;
for/while-do loop {
if (conditions) { break label; }
}
statement(s)
| Break Statement (labeled break) |
for/while-do loop {
if (conditions) { continue; }
}
| Continue Statement: goes back to the loop condition |
return;
return variable;
| Exist the program with or without returning a value |
| Classes | |
public class class_name {
fields
constructor
methods
}
| Structure, constructor builds initial fields, methods acts on fields in application of the class |
class MyClass extends MySuperClass implements YourInterface {
fields
constructor
methods
}
| Extends an existing class |
public class class_name {
privat:
fields
public:
constructor
methods
}
| Differentates between public and privat fields/methods |
methods ()
methods (int x)
| Posibility of calling the same method in different ways (Overloading Methods) |
public class Point {
public int x = 0;
public int y = 0;
//constructor
public Point(int a, int b) {
x = a;
y = b;
}
}
| Initializing an Object; declaration uses the same name as the class and it has no return type |
objectReference.methodName(argumentList);
| Call a method |
public class Point {
public int x = 0;
public int y = 0;
//constructor
public Point(int x, int y) {
this.x = x;
this.y = y;
}
}
| Us of this with a Field |
public class Rectangle {
private int x, y;
private int width, height;
public Rectangle() {
this(0, 0, 0, 0);
}
public Rectangle(int width, int height) {
this(0, 0, width, height);
}
public Rectangle(int x, int y, int width, int height) {
this.x = x;
this.y = y;
this.width = width;
this.height = height;
}
...
}
| Use of this with a Constructor |
class OuterClass {
...
class NestedClass {
...
}
}
| Nested Class |
OuterClass.InnerClass innerObject = outerObject.new InnerClass();
| Call in a Nested Class |
| Special commants | |
JOptionPane.showMessageDialog(frame, text, "Warning",JOptionPane.WARNING_MESSAGE);
| Message Popup |
@Author(
name = "Benjamin Franklin",
date = "3/27/2003"
)
| Author of the code |
@SuppressWarnings(value = "unchecked")
void myMethod() { }
| Suppress compilation warnings |
@Override
int overriddenMethod() { }
| Override existing methods |
@Deprecated
static void deprecatedMethod() { }
| Warning at compliation if old function is used |
| Signed Applet | Oracle, Tutorial, Chapter 10 |
javac {java-program}.java
|
Compile the Applet |
jar cvf {java-applet}.jar {java-program}.class
|
Make a JAR File |
keytool -genkey -alias signFiles -keystore {local_store}
-keypass {key password} -dname "cn={name}"
-storepass {store password}
|
Generate Keys |
jarsigner -keystore {local_store} -storepass {store password}
-keypass {key password}
-signedjar
S{java-applet}.jar {java-applet}.jar signFiles
|
Sign the JAR File |
keytool -export -keystore {local_store} -storepass {store password}
-alias signFiles -file {company_certificate}.cer
|
Export the Public Key Certificate |
keytool -import -alias company -file {company_certificate}.cer
-keystore {customer_store} -storepass {customer_password}
|
Import Certificate as a Trusted Certificate |
Java
