Pattern

Use Pattern.compile(String regex) to create a Pattern object.

Pattern pat1 = Pattern.compile("cat|dog|frog");

* This will match any of the alternatives, cat or dog or frog.

You can split a string with Pattern.split(CharSequence c).

Your regex defines the delimiter on which to split.

Pattern p = Pattern.compile("[|]"); 
String[] words = p.split("This|is|a|test.");

* This will split on the | character in the data - in the pattern, | is in square brackets making it a literal.

For a single-use pattern match:

boolean b = Pattern.matches("^Kha{3,}n!+", someString);

To set regex options, use Pattern.compile(String regex, int flags)

The Pattern class defines a number of standard regex options including:

Flag	Usage
CASE_INSENSITIVE	Allows case-insensitive matching.
COMMENTS	Allows white space and comments in a pattern.
MULTILINE	Searches for patterns in a multiline string.

The following will match text starting with "CAT", "Cat", "cat", etc. . .
```
Pattern p = Pattern.compile("^cat", Pattern.CASE_INSENSITIVE);
```

Combine multiple options with the bitwise-or operator:

Pattern p = Pattern.compile("^cat", Pattern.CASE_INSENSITIVE | Pattern.MULTILINE);

Practice Exercise¶

bitwise-or

When used in a numeric expression, the | operator yields a number with all of the bits that are set in either of its operands:
int a = 4;          // 0b00000100
int b = 16;         // 0b00010000
int result = a | b; // 0b00010100, or 20
This can be a convenient way to pass a list of options to a method, without having to define a separate method parameter for each option.

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