java11-pattern-asMatchPredicate-vs-asPredicate

Pattern: asMatchPredicate() vs asPredicate() investigation.

project description

Since java 11 we have two methods in Pattern class transforming pattern matching to a Predicate:

• asMatchPredicate() - Creates a predicate that tests if this pattern matches a given input string.

  public Predicate<String> asMatchPredicate() {
      return s -> matcher(s).matches();
  }
  

• asPredicate() - Creates a predicate that tests if this pattern is found in a given input string.

  public Predicate<String> asPredicate() {
      return s -> matcher(s).find();
  }
  

  remark: Note that find() returns true if, and only if, a subsequence of the input sequence matches this matcher's pattern

tests

• asMatchPredicate()

  Predicate<String> validator = Pattern.compile("[a-z]").asMatchPredicate();
  
  assertFalse(validator.test("1"));
  assertTrue(validator.test("a"));
  assertFalse(validator.test("111a"));
  

• asPredicate()

  Predicate<String> validator = Pattern.compile("[a-z]").asPredicate();
  
  assertFalse(validator.test("1"));
  assertTrue(validator.test("a"));
  assertTrue(validator.test("111a"));
  

Remark: so the only difference between two methods mentioned above is when it comes to substrings:

assertFalse(asMatchPredicate.test("111a"));
assertTrue(asPredicate.test("111a"));