This example will determine how to count the number of digits contained within a string using java, java 8 and Google guava. Each snippet below will check if a string is a number then increment a counter validating that there are 4 numbers using junit assertEquals.
Straight up Java
@Test
public void digits_in_string_guava_java() {
String phrase = "Creating xml using java gives me heart burn, "
+ "hopefully java 8, java 9, java 10 address this";
int numberOfDigits = 0;
char[] checkForNumbers = phrase.toCharArray();
for (char val : checkForNumbers) {
if (Character.isDigit(val)) {
numberOfDigits++;
}
}
assertEquals(4, numberOfDigits);
}Java 8
@Test
public void digits_in_string_guava_java8() {
String phrase = "Creating xml using java gives me heart burn, "
+ "hopefully java 8, java 9, java 10 address this";
assertEquals(4, phrase.chars().filter(Character::isDigit).count());
}Google Guava
@Test
public void digits_in_string_guava() {
String phrase = "Creating xml using java gives me heart burn, "
+ "hopefully java 8, java 9, java 10 address this";
String numberOfDigits = CharMatcher.DIGIT.retainFrom(phrase);
assertEquals(4, numberOfDigits.length());
}