ImperativeCharSummarizer.java

var totalDigits = 0;
var totalUppercaseChars = 0;
var totalLowercaseChars = 0;
var totalInvalidChars = 0;
for (final char current : string.toCharArray()) {
    if (Character.isDigit(current)) {
        totalDigits += 1;
    } else if (Character.isUpperCase(current)) {
        totalUppercaseChars += 1;
    } else if (Character.isLowerCase(current)) {
        totalLowercaseChars += 1;
    } else {
        totalInvalidChars += 1;
    }
}