java regex alphanumeric and special characters

regular expressions (regex) in java are a powerful way to define patterns for string matching and manipulation. in this tutorial, we will explore how to use regex to work with alphanumeric characters and special characters.

### what are alphanumeric characters?

alphanumeric characters include:
- letters (a-z, a-z)
- digits (0-9)

### what are special characters?

special characters include any characters that are not alphanumeric, such as punctuation marks, symbols, whitespace, etc. for example: `!@#$%^&*()_+-=[]{}|;:'",.?/`.

### basic regex patterns

1. **alphanumeric characters**:
- pattern: `[a-za-z0-9]`
- this matches any single alphanumeric character.

2. **special characters**:
- pattern: `[^a-za-z0-9]`
- this matches any character that is not alphanumeric.

3. **any character**:
- pattern: `.` (dot)
- this matches any single character except for a newline.

### java regex example

let's create a simple java program that demonstrates how to use regex to identify and categorize alphanumeric and special characters in a string.

### explanation of the code

2. **input string**: we define an input string that contains a mix of alphanumeric and special characters.

3. **alphanumeric pattern**:
- we compile a regex pattern that matches any alphanumeric character: `[a-za-z0-9]`.
- we use `matcher` to find all occurrences of this pattern in the input string.

4. **display alphanumeric characters**: we iterate over the matches and print each alphanumeric character.

5. **special character pattern**:
- we compile a regex pattern that matches any character that is not alphanumeric or whitespace: `[^a-za-z0-9\\s]`.
- again, we use `matcher` to find all occurrences of this pattern in the input string.

6. **display special characters**: we iterate over the matches and print each special character.

### output of the program

when you run th ...

#python alphanumeric regex
#python alphanumeric
#python alphanumeric hash
#python alphanumeric generator
#python alphanumeric only

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