I have a method to remove some characters from a string. Is there a better way to do this using java 8?
public String filter(String test) {
StringBuilder builder = new StringBuilder();
for (int i = 0; i < test.length(); i++) {
if (MYCOLLECTION.contains(test.charAt(i))) {
builder .append(test.charAt(i));
}
}
return builder .toString();
}
How about this:
Set<Character> filter = new HashSet<>(Arrays.asList('a','b','c'));
String filtered = "abcdefga".chars ()
.filter(i -> filter.contains((char) i))
.mapToObj(i -> "" + (char) i)
.collect(Collectors.joining());
System.out.println (filtered);
Output:
abca
Note: filter serves the same purpose as your MYCOLLECTION - I just gave it a more meaningful name and used a Set for better performance of contains.
It could have been cleaner if there was a CharStream (i.e. stream of primitive chars), so I wouldn't have to use an IntStream.
.mapToObj(Character::toString) over .mapToObj(i -> "" + (char) i), right?
.mapToObj(i -> Character.toString((char) i)). The suggested method reference doesn't pass compilation.
Character.toString(int) has been added in Java 11.filtered = inputString.replaceAll( filter.stream().map(Object::toString).collect(Collectors.joining("", "[^", "]")),"")? It only works when the characters have no special meaning (or you’d need additional efforts). Unless the filter characters are constant, nothing can beat the simple loop solution…"Better" by what metric? Here's how I would write it
final String filtered = test.chars()
.mapToObj(chr -> (char) chr) // IntStream -> Stream<Character>
.filter(MYCOLLECTION::contains)
.collect(
Collector.of(StringBuilder::new, StringBuilder::append, StringBuilder::append, StringBuilder::toString)
);
The collector is a bit ugly, I would probably extract it to its own method
private static Collector<Character, StringBuilder, String> characterCollector()
{
return Collector.of(
StringBuilder::new,
StringBuilder::append,
StringBuilder::append,
StringBuilder::toString
);
}
Then call this instead
.collect(characterCollector())
If you're open to using a third-party library, the following will work using Java 8 with Eclipse Collections.
CharSet set = CharSets.immutable.with('a', 'b', 'c');
CharAdapter chars = Strings.asChars("a1b2c3");
String string = chars.select(set::contains).toString();
Assert.assertEquals("abc", string);
Eclipse Collections has support for primitive collections so there is no need to box char values as Character instances.
You can also exclude instead of include characters using the method named reject which is the opposite of select.
CharSet set = CharSets.immutable.with('a', 'b', 'c');
CharAdapter chars = Strings.asChars("a1b2c3");
String include = chars.select(set::contains).toString();
String exclude = chars.reject(set::contains).toString();
Assert.assertEquals("abc", include);
Assert.assertEquals("123", exclude);
Note: I am a committer for Eclipse Collections.
Here is a very simple way using Regex
var string = "what ever you want!";
final var charSet = "".,;:!@";
final var stringResult = string.replaceAll("[" + charSet + "]", "");
>> ""what ever you want"
