Feature required in #73 (#77)

Author: Cs4r

src/main/java/strman/Strman.java

@@ -34,6 +34,9 @@
 import java.util.regex.Pattern;
 import java.util.stream.Stream;
 
+import static java.util.function.Function.identity;
+import static java.util.stream.Collectors.counting;
+import static java.util.stream.Collectors.groupingBy;
 import static java.util.stream.Collectors.joining;
 
 /**
@@ -87,7 +90,7 @@ public static String appendArray(final String value, final String[] appends) {
  * @return an Optional String if found else empty
  */
  public static Optional<String> at(final String value, int index) {
- if (value == null || value.isEmpty()) {
+ if (isNullOrEmpty(value)) {
  return Optional.empty();
  }
  int length = value.length();
@@ -97,6 +100,10 @@ public static Optional<String> at(final String value, int index) {
  return (index < length && index >= 0) ? Optional.of(String.valueOf(value.charAt(index))) : Optional.empty();
  }
 
+ private static boolean isNullOrEmpty(String input) {
+ return input == null || input.isEmpty();
+ }
+
  /**
  * Returns an array with strings between start and end.
  *
@@ -1302,4 +1309,20 @@ private static long countSubstr(String value, String subStr, boolean allowOverla
  }
  return countSubstr(value.substring(offset), subStr, allowOverlapping, ++count);
  }
+
+ /**
+ * Counts the number of occurrences of each character in the string
+ *
+ * @param input The input string
+ * @return A map containing the number of occurrences of each character in the string
+ */
+ public static Map<Character, Long> charsCount(String input) {
+ if (isNullOrEmpty(input)) {
+ return Collections.emptyMap();
+ }
+
+ return input.chars()
+ .mapToObj(c -> (char) c)
+ .collect(groupingBy(identity(), counting()));
+ }
 }

src/test/java/strman/StrmanTest.java

@@ -29,8 +29,7 @@
 import org.junit.Ignore;
 import org.junit.Test;
 
-import java.util.Arrays;
-import java.util.Optional;
+import java.util.*;
 
 import static java.util.stream.Collectors.toList;
 import static org.hamcrest.CoreMatchers.*;
@@ -990,4 +989,42 @@ public void trimEnd_shouldRemoveAllTrailingSpecialCharacters() throws Exception
  assertThat(trimEnd("-_-abc!-_-", "_", "-", "!"), is(Optional.of("-_-abc")));
  assertThat(trimEnd("-_-abc#-_-", "_", "-", "!", "#"), is(Optional.of("-_-abc")));
  }
+
+
+ @Test
+ public void charsCount_shouldReturnEmptyWhenInputStringIsNull(){
+ assertThat(charsCount(null), equalTo(Collections.emptyMap()));
+ }
+
+ @Test
+ public void charsCount_shouldReturnEmptyWhenInputStringIsEmpty(){
+ assertThat(charsCount(""), equalTo(Collections.emptyMap()));
+ }
+
+ @Test
+ public void charsCount_shouldReturnCharsCountWhenInputIsASimpleString(){
+ Map<Character, Long> expectedOutput = new HashMap<Character, Long>(){{
+ put('a',1L);
+ put('b', 1L);
+ put('c', 1L);
+ }};
+
+ assertThat(charsCount("abc"), equalTo(expectedOutput));
+ }
+
+ @Test
+ public void charsCount_shouldReturnCharsCountWhenInputIsAComplexString(){
+ Map<Character, Long> expectedOutput = new HashMap<Character, Long>(){{
+ put('a',1L);
+ put('b', 2L);
+ put('c', 3L);
+
+ put('A',1L);
+ put('B', 2L);
+ put('C', 3L);
+ put('-', 10L);
+ }};
+
+ assertThat(charsCount("-----abbcccCCCBBA-----"), equalTo(expectedOutput));
+ }
 }