Islamic University of Gaza Faculty of Engineering

Department of Computer Engineering ECOM 2124: JAVA II Lab

Lab # 2

Regular Expressions

&

Command Line Arguments

Eng. Haneen El-Masry

February, 2014

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Objective

To be familiar with Regular Expressions and Command Line Arguments.

Regular Expression

A regular expression (regex) is a string that describes a pattern for matching a set of

strings. Regular expression is a powerful tool for string manipulations. You can use

regular expressions for matching, replacing, and splitting strings.

Regular Expression Syntax

A regular expression consists of literal characters and special symbols.

Example 1: Strings Matching

Example 1 shows matching strings using some frequently used syntax for regular

expressions.

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The Output:

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Example 2:

Write a java program that prompts the user to enter his name that must consist of first

name and last name separated by space, such that the first and last name consists of at

most twenty five letters, then if the name satisfied its pattern, let the user to enter his

phone number that must be ten digits. If there is an error, notify the user.

The Output:

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Example 3: Strings Replacing & Splitting

The Output:

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Command-Line Arguments

The main method has parameter args of String[] type. The main method is just a regular

method. Furthermore, You can pass strings to the main method from the command line

when you run the program. Strings passed to the main program are stored in args. The

first string is represented by args[0], and args.length is the number of strings passed.

Note: The strings are separated by a space. A string that contains a space must be

enclosed in double quotes.

Example 4:

Write a program passes an unspecified number of integers as separate strings to the

main method and displays their total.

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To run a NetBeans program from the Command Line, Follow the following steps:

1- File >> Project Properties.

2- Choose Run category.

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3- In Main class, browse for the program you wanted to run >> select Main Class.

4- Press OK.

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5- Run >> Clean and Build Project.

6- Copy the run command from NetBeans' Output window.

7- Open Command Window and set the path to JDK bin directory path.

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8- Paste the run command that you copied, and follow it by main method

arguments >> Enter.

Here, main method

Arguments must be.

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Exercises

1- (Checking password) Some Websites impose certain rules for passwords. Write

a method that checks whether a string is a valid password. Suppose the

password rule is as follows:

A password must have at least eight characters.

A password consists of only letters and digits.

A password must contain at least two digits.

Write a program that prompts the user to enter a password and displays "Valid

Password" if the rule is followed or "Invalid Password" otherwise.

2- (Finding the number of uppercase letters in a string) Write a program that

passes a string to the main method and displays the number of uppercase

letters in a string.

BONUS

(Sorting characters in a string) Write a method that returns a sorted string using

the following header:

public static String sort (String s)

For example, sort("acb") returns abc.

Write a test program that prompts the user to enter a string and displays the

sorted string.

Hint: You can use StringBuilder class and its methods.

Best Wishes