How to escape special characters in Java regex

How to escape special characters in Java regex

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In Java regular expressions (regex), certain characters have special meanings. For example, the dot (.) matches any character except a newline, and the star (*) means "zero or more occurrences of the preceding element." However, sometimes you might want to match these special characters literally, rather than using their special meanings.

To escape special characters in Java regex, you can use a backslash () followed by the special character. For example, if you want to match a dot (.) literally, you would use "." This is called an "escape sequence."

Here are some common special characters and how to escape them:

Here are some examples of using escaped special characters in regex:

// Match a literal dot (.)
String pattern = ".";
Pattern p = Pattern.compile(pattern);
// Match one or more occurrences of the letter "a" literally
String pattern = "a*";
Pattern p = Pattern.compile(pattern);
// Match the string "hello" followed by an optional comma and space
String pattern = "hello(, ?s*)?";
Pattern p = Pattern.compile(pattern);

In addition to escaping special characters, you can also use character classes (also known as character sets) to match a set of characters. A character class is denoted by square brackets [] and contains a list of characters that you want to match.

For example:

// Match any uppercase or lowercase letter
String pattern = "[a-zA-Z]";
Pattern p = Pattern.compile(pattern);
// Match any digit (0-9)
String pattern = "d";
Pattern p = Pattern.compile(pattern);

In Java regex, there are also some special sequences that can be used to match certain characters. These include:

Here are some examples of using these special sequences:

// Match a word that starts with "un" and ends with "ly"
String pattern = "bunw+lyb";
Pattern p = Pattern.compile(pattern);
// Match the end of the string
String pattern = "worldZ";
Pattern p = Pattern.compile(pattern);

In summary, to escape special characters in Java regex, you can use a backslash () followed by the special character. Additionally, you can use character classes and special sequences to match certain characters or groups of characters.

I hope this helps!

Special characters in string java w3schools

I'll respond in English as per your request!

String manipulation is a fundamental concept in programming languages like Java. In this response, I'll focus on the basics of strings and demonstrate how to use various methods provided by Java's String class.

What are Strings in Java?

In Java, a string is a sequence of characters that can be used as a variable or passed as an argument to a method. The String class provides a set of methods for manipulating strings, such as concatenation, substring extraction, and searching.

Java String Methods:

Here's a list of some essential methods in the Java String class:

String str1 = "Hello";
String str2 = "World!";
String result = str1.concat(str2);
System.out.println(result);  // Output: HelloWorld!

String str = "Java is awesome";
String subset = str.substring(6, 11);  // Output: is awe
System.out.println(subset);

String str1 = "Java";
String searchStr = "va";
int index = str1.indexOf(searchStr, 0);  // Output: 1
System.out.println(index);

String str = "hello";
String result = str.toUpperCase();  // Output: HELLO
System.out.println(result);

String str = "   Hello   ";
String result = str.trim();
System.out.println(result);  // Output: Hello

Special Characters in String Manipulation:

Java strings can include special characters like:

These special characters are used to create formatted output, for example:

String str = "Line 1nLine 2";
System.out.println(str);  // Output: Line 1 Line 2
String tabStr = "Tabulated texttMore text";
System.out.println(tabStr);  // Output: Tabulated text    More text

These are just a few examples of the many methods and special characters available in Java's String class. Mastering these concepts will help you to efficiently work with strings in your Java applications.

Hope this response helps you!