$re = '/(((import java\.)[a-zA-Z\.\*]*;)|(public static void main(.*))|(class\s[a-zA-Z_$]+[\s]*\{)|(System\.out\.print))/';
$str = '/*
Calculate Circle Area using Java Example
This Calculate Circle Area using Java Example shows how to calculate
area of circle using it\'s radius.
*/
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
public class CalculateCircleAreaExample {
public static void main(String[] args) {
int radius = 0;
System.out.println("Please enter radius of a circle");
try
{
//get the radius from console
BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
radius = Integer.parseInt(br.readLine());
}
//if invalid value was entered
catch(NumberFormatException ne)
{
System.out.println("Invalid radius value" + ne);
System.exit(0);
}
catch(IOException ioe)
{
System.out.println("IO Error :" + ioe);
System.exit(0);
}
/*
* Area of a circle is
* pi * r * r
* where r is a radius of a circle.
*/
//NOTE : use Math.PI constant to get value of pi
double area = Math.PI * radius * radius;
System.out.println("Area of a circle is " + area);
}
}
/*
Output of Calculate Circle Area using Java Example would be
Please enter radius of a circle
19
Area of a circle is 1134.1149479459152
*/
@@@@
/*
Calculate Rectangle Area using Java Example
This Calculate Rectangle Area using Java Example shows how to calculate
area of Rectangle using it\'s length and width.
*/
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
public class CalculateRectArea {
public static void main(String[] args) {
int width = 0;
int length = 0;
try
{
//read the length from console
BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
System.out.println("Please enter length of a rectangle");
length = Integer.parseInt(br.readLine());
//read the width from console
System.out.println("Please enter width of a rectangle");
width = Integer.parseInt(br.readLine());
}
//if invalid value was entered
catch(NumberFormatException ne)
{
System.out.println("Invalid value" + ne);
System.exit(0);
}
catch(IOException ioe)
{
System.out.println("IO Error :" + ioe);
System.exit(0);
}
/*
* Area of a rectangle is
* length * width
*/
int area = length * width;
System.out.println("Area of a rectangle is " + area);
}
}
/*
Output of Calculate Rectangle Area using Java Example would be
Please enter length of a rectangle
10
Please enter width of a rectangle
15
Area of a rectangle is 150
*/
@@@@
/*
Java Factorial Using Recursion Example
This Java example shows how to generate factorial of a given number
using recursive function.
*/
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
public class JavaFactorialUsingRecursion {
public static void main(String args[]) throws NumberFormatException, IOException{
System.out.println("Enter the number: ");
//get input from the user
BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
int a = Integer.parseInt(br.readLine());
//call the recursive function to generate factorial
int result= fact(a);
System.out.println("Factorial of the number is: " + result);
}
static int fact(int b)
{
if(b <= 1)
//if the number is 1 then return 1
return 1;
else
//else call the same function with the value - 1
return b * fact(b-1);
}
}
/*
Output of this Java example would be
Enter the number:
5
Factorial of the number is: 120
*/
@@@@
/*
Swap Numbers Without Using Third Variable Java Example
This Swap Numbers Java Example shows how to
swap value of two numbers without using third variable using java.
*/
public class SwapElementsWithoutThirdVariableExample {
public static void main(String[] args) {
int num1 = 10;
int num2 = 20;
System.out.println("Before Swapping");
System.out.println("Value of num1 is :" + num1);
System.out.println("Value of num2 is :" +num2);
//add both the numbers and assign it to first
num1 = num1 + num2;
num2 = num1 - num2;
num1 = num1 - num2;
System.out.println("Before Swapping");
System.out.println("Value of num1 is :" + num1);
System.out.println("Value of num2 is :" +num2);
}
}
/*
Output of Swap Numbers Without Using Third Variable example would be
Before Swapping
Value of num1 is :10
Value of num2 is :20
Before Swapping
Value of num1 is :20
Value of num2 is :10
*/
@@@@
// OddEven.java
import javax.swing.JOptionPane;
public class OddEven {
/**
* "input" is the number that the user gives to the computer
*/
private int input; // a whole number("int" means integer)
/**
* This is the constructor method. It gets called when an object of the OddEven type
* is being created.
*/
public OddEven() {
/*
* In most Java programs constructors can initialize objects with default values, or create
* other objects that this object might use to perform its functions. In some Java programs, the
* constructor may simply be an empty function if nothing needs to be initialized prior to the
* functioning of the object. In this program\'s case, an empty constructor would suffice.
* A constructor must exist; however, if the user doesn\'t put one in then the compiler
* will create an empty one.
*/
}
/**
* This is the main method. It gets called when this class is run through a Java interpreter.
* @param args command line arguments (unused)
*/
public static void main(final String[] args) {
/*
* This line of code creates a new instance of this class called "number" (also known as an
* Object) and initializes it by calling the constructor. The next line of code calls
* the "showDialog()" method, which brings up a prompt to ask you for a number
*/
OddEven number = new OddEven();
number.showDialog();
}
public void showDialog() {
/*
* "try" makes sure nothing goes wrong. If something does,
* the interpreter skips to "catch" to see what it should do.
*/
try {
/*
* The code below brings up a JOptionPane, which is a dialog box
* The String returned by the "showInputDialog()" method is converted into
* an integer, making the program treat it as a number instead of a word.
* After that, this method calls a second method, calculate() that will
* display either "Even" or "Odd."
*/
this.input = Integer.parseInt(JOptionPane.showInputDialog("Please enter a number."));
this.calculate();
} catch (final NumberFormatException e) {
/*
* Getting in the catch block means that there was a problem with the format of
* the number. Probably some letters were typed in instead of a number.
*/
System.err.println("ERROR: Invalid input. Please type in a numerical value.");
}
}
/**
* When this gets called, it sends a message to the interpreter.
* The interpreter usually shows it on the command prompt (For Windows users)
* or the terminal (For *nix users).(Assuming it\'s open)
*/
private void calculate() {
if ((this.input % 2) == 0) {
JOptionPane.showMessageDialog(null, "Even");
} else {
JOptionPane.showMessageDialog(null, "Odd");
}
}
}';
preg_match_all($re, $str, $matches, PREG_SET_ORDER, 0);
// Print the entire match result
var_dump($matches);
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for PHP, please visit: http://php.net/manual/en/ref.pcre.php