String objects of Java and PHP Part 4

Strings of Java and PHP

This is the fourth part of the Introduction to Java and PHP series. String objects of Java and PHP will be discussed. Whenever possible, code examples will be made in a similar manner for both Java and PHP.

Strings in Java and PHP are very similar. Variables in Java and PHP can declared and assigned values at the same time.

In this tutorial, Java and PHP will be used to create a program consisting of string expressions. The program will be compiled and executed. In order to make the work-flow faster, please use a programming editor.

Text editor for creating and modifying the Java and PHP files.
Java.
PHP.

Optional Download and install suitable text editor

Any text editor will work. A bare minimum should be syntax-highlighting for Java and PHP. To select a reviewed lightweight programming editor read the Ojambo.com Lightweight Programming Editors.

Lesson 15: Declare String Variables

Java	PHP
String string1 = new String(); // String String string1 = “abc”; // String String string2 = “def”; // String String string3 = ” leading and trailing whitespace “; // String	$string1; // String $string1 = “abc”; // String $string2 = “def”; // String $string3 = ” leading and trailing whitespace “; // String

In Java, strings are constant and represents by the class “String”. Java also requires the variable’s first letter to be lowercase.
PHP only requires the variable to have a dollar sign at the beginning.

Lesson 16: String Copy

Java	PHP
String stringCopy = new String(string1); // String as new variable	$stringCopy = $string1; // String as new variable

In Java, the new string variable is created as a new object. In PHP, a new string variable only requires the dollar sign at the beginning.

Lesson 17: String Concatenation

Java	PHP
String stringCat = string1 + string2; // String concatenation	$stringCat = $string1 . $string2; // String concatenation

For Java, the string concatenation operator is the plus sign “+”. In PHP, the string concatenation operator is the period sign “.”.

Lesson 18: String Manipulation

Java	PHP
Substring (String Substitute)
String stringSub = string1.substring(2,3); // Substring(from, to)	$StringSub = substr($string1, 2,3); // Substr(string, start, length)
Uppercase
String stringUpper = string1.toUpperCase(); // Uppercase	$stringUpper = strtoupper($string1); // Uppercase
Trim (Remove Whitespace)
String stringTrim = string3.trim(); // Trim whitespace	$stringTrim = trim($string3); // Trim whitespace

Java uses substring with a specified start index and an optional end index for string substitution. PHP uses substr with a specified string, start, and an optional length for string substitution. For string substitution, both Java and PHP use integers to specify the start and length.

Java uses toUpperCase to convert a string to uppercase. PHP uses strtoupper with a specified string in order to convert a string to uppercase.

Java uses trim to remove leading and trailing whitespace. PHP uses trim with a specified string in order to remove leading and trailing whitespace.

StringObjects.java file

/**
 * Ojambo.com String Objects Java Tutorial
 * StringObjects.java Copyright 2011 Edward
 * http://www.ojambo.com
 * 
 */
 
// This class displays String Objects
public class StringObjects { //This class is called StringObjects
    public static void main(String[] args) { // Main Method
        // Declare variables and assign values immediately 
	    String string1 = "abc"; // String
		String string2 = "def"; // String
		String string3 = " leading and trailing whitespace "; // String
            
        // Concatenation 
        String stringCat = string1 + string2; // Concatenate string1 plus string2
        
        // String Substitution
		String stringSub = string1.substring(2,3); // Substring(from, to)
        // String Uppercase
        String stringUpper = string1.toUpperCase(); // Uppercase convert
        // Remove Whitespace
        String stringTrim = string3.trim(); // Trim whitespace
            
        // Print out the assigned variables;
        System.out.println("string1 is " + string1); // Print the variable string1
        System.out.println("string2 is " + string2); // Print the variable string2
        System.out.println("string3 is " + string3); // Print the variable string3
        System.out.println("stringCat is " + stringCat); // Print the variable stringCat
        System.out.println("stringSub is " + stringSub); // Print the variable stringSub
        System.out.println("stringUpper is " + stringUpper); // Print the variable stringUpper
        System.out.println("stringTrim is " + stringTrim); // Print the variable stringTrim
    }
}

The StringObjects.java file can be compiled as javac StringObjects.java and executed with java StringObjects.

StringObjects.php file

<?php
/*
 * Ojambo.com String Objects PHP Tutorial
 * StringObjects.php Copyright 2011 Edward
 * http://www.ojambo.com
 * 
 */
 
	// Declare variables and assign values immediately 
	$string1 = "abc"; // String
	$string2 = "def"; // String
	$string3 = " leading and trailing whitespace "; // String
		
	// Concatenation 
	$stringCat = $string1 + $string2; // Concatenate string1 plus string2
	
	// $substitution
	$stringSub = substr($string1,2,3); // Substr(string, start, length)
	// String Uppercase
	$stringUpper = strtoupper($string1); // Uppercase convert
	// Remove Whitespace
	$stringTrim = trim($string3); // Trim whitespace

	// These statements print the assigned variables
	echo "string1 is".$string1; // Print out the $string1 variable
	echo "string2 is".$string2; // Print out the $string2 variable
	echo "string3 is".$string3; // Print out the $string3 variable
	echo "stringCat is".$stringCat; // Print out the $stringCat variable
	echo "stringSub is".$stringSub; // Print out the $stringSub variable
	echo "stringUpper is".$stringUpper; // Print out the $stringUpper variable
	echo "stringTrim is".$stringTrim; // Print out the $stringTrim variable

?>

The StringObjects.php can be compiled as php -l StringObjects.php and compiled with php StringObjects.php

Conclusion:

Java variables must begin with a lowercase letter. In Java, every variable must be specifically declared while PHP only requires a dollar sign. Sometimes Java and PHP share the same String Objects such as the trim function.

Java and PHP have the same string functions with different names. For example, concatenation is the plus sign in Java, but a period sign in PHP. String substitution is handled by the substring object in Java and substr fucntion is PHP. In order to convert strings into uppercase, Java uses the toUpperCase object and PHP uses strtoupper function.

This tutorial uses an optional lightweight programming editor with syntax-highlighting features.
The concepts taught in the first eighteen lessons can be applied to other programming languages.
When selecting a programming language to master, pay close attention to license restrictions.