Advanced Programming

Collage of Information

Technology University of Palestine, Gaza

Prepared by:

Mahmoud Rafeek Alfarra

Lecture 16: Working with Text (1)

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قالوا

قال رسول الله صلى الله عليه و سلم:

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Outlines

Why working with Text ?

How Java supports working with Text?

String class and its methods

The Collator class

Parsing

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Introduction

Organizations see the Internet and the Web as crucial to their information-systems strategies.

Java provides a number of built-in networking capabilities.

Java can enable programs to search the world for information and to collaborate with programs running on other computers internationally.

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How does Java support working with Text?

The Java Application Programming Interface (API) contains two packages which are:

1.java.text : contains the international text classes.

2.java.util.regex: contains classes to work with regular expressions

And the package java.lang which contains the basic language classes as String class

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String class

Many methods:

1.String.valueOf( );

2.Thing.toString( );

3.equals( );

4.compareTo( ); // method compares strings strictly by their characters' positions in the Unicode specification.

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The Collator class

The java.text package provides a sophisticated set of classes for comparing strings in specific languages.

You can obtain a default Collator by calling the Collator.getInstance( ) method with no arguments.

Once you have an appropriate Collator instance, you can use its compare( ) method, which returns values just like String's compareTo( ) method.

Using collators is essential if you're working with languages other than English.

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String class/search

The String class provides several simple methods for finding fixed substrings within a string.

1. startsWith( ): Compares an argument string with the beginning of the String

2. endsWith( ): Compares an argument string with end of the String

3. indexOf( ): Searches for the first occurrence of a character or substring and returns the starting character position, or -1 if the substring is not found:

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String class/search

4. lastIndexOf( ) : searches backward through the string for the last occurrence of a character or substring.

5. contains( ) : checking to see whether a given substring is contained in the target string

For more complex searching, you can use the Regular Expression API

We will study RegExp in the next lecture isa

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A number of methods operate on the String and return a new String as a result.

1. trim( ): Removes leading and trailing whitespace (i.e., carriage return, newline, and tab) from the String.

2. toUpperCase( ) and toLowerCase( ) methods return a new String of the appropriate case

3. substring( ): returns a specified range of characters.

String class/Editing

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4. replace( ): One or more occurrences of the target string are replaced with the replacement string, moving from beginning to end.

String class/Editing

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String methods

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String methods

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StringBuilder

The java.lang.StringBuilder class is a modifiable and expandable buffer for characters. You can use it to create a big string efficiently.

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Parsing Primitive Numbers Java has a rich set of APIs for parsing and printing

formatted strings, including numbers, dates, times, and currency values.

For numbers and Booleans, Each of these primitive wrapper classes has a static "parse" method that reads a String and returns the corresponding primitive type. For example:

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Parsing Primitive Numbers java.util.Scanner provides a single API for not

only parsing individual primitive types from strings, but reading them from a stream of tokens.

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Parsing a string of text A common programming task involves parsing a

string of text into words or "tokens" that are separated by some set of delimiter characters, such as spaces or commas.

Parse this by the following codesingle whitespace character

single whitespace character

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Parsing a string of text With the new Scanner API, we could go a step

further and parse the numbers of our second example as we extract them:

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Parsing a string of text StringTokenizer allows you to specify a delimiter

as a set of characters and matches any number or combination of those characters as a delimiter between tokens.

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Next Lecture isa

Regular Expressions