Fixed #19. Added support for removeLeft function

src/main/java/strman/Strman.java

@@ -1,6 +1,7 @@
 package strman;
 
 import java.util.*;
+import java.util.function.BiFunction;
 import java.util.function.Predicate;
 import java.util.function.Supplier;
 import java.util.regex.Matcher;
@@ -667,6 +668,35 @@ public abstract class Strman {
         return Arrays.stream(strings).filter(str -> str != null && !str.trim().isEmpty()).toArray(String[]::new);
     }
 
+    /**
+     * Returns a new String with the prefix removed, if present. This is case sensitive.
+     *
+     * @param value  The input String
+     * @param prefix String to remove on left
+     * @return The String without prefix
+     */
+    public static String removeLeft(final String value, final String prefix) {
+        return removeLeft(value, prefix, true);
+    }
+
+    /**
+     * Returns a new String with the prefix removed, if present.
+     *
+     * @param value         The input String
+     * @param prefix        String to remove on left
+     * @param caseSensitive ensure case sensitivity
+     * @return The String without prefix
+     */
+    public static String removeLeft(final String value, final String prefix, final boolean caseSensitive) {
+        validate(value, NULL_STRING_PREDICATE, NULL_STRING_MSG_SUPPLIER);
+        validate(prefix, NULL_STRING_PREDICATE, NULL_STRING_MSG_SUPPLIER);
+        BiFunction<String, String, String> fx = (f, s) -> f.startsWith(s) ? f.replace(s, "") : f;
+        if (caseSensitive) {
+            return fx.apply(value, prefix);
+        }
+        return fx.apply(value.toLowerCase(), prefix.toLowerCase());
+    }
+
     public static String decode(final String value, final int digits, final int radix) {
         validate(value, NULL_STRING_PREDICATE, NULL_STRING_MSG_SUPPLIER);
         return Arrays

src/test/java/strman/StrmanTest.java

@@ -504,4 +504,24 @@ public class StrmanTest {
         assertThat(removeEmptyStrings(new String[]{"aa", "", "   ", "bb", "cc", null}), arrayContaining("aa", "bb", "cc"));
         assertThat(removeEmptyStrings(new String[0]), emptyArray());
     }
+
+    @Test
+    public void removeLeft_shouldRemoveStringFromLeft() throws Exception {
+        final String[] fixture = {
+                "foobar",
+                "bar"
+        };
+
+        Arrays.stream(fixture).forEach(el -> assertThat(removeLeft(el, "foo"), equalTo("bar")));
+    }
+
+    @Test
+    public void removeLeft_shouldRemoveStringFromLeftCaseInSensitive() throws Exception {
+        final String[] fixture = {
+                "foobar",
+                "bar"
+        };
+
+        Arrays.stream(fixture).forEach(el -> assertThat(removeLeft(el, "FOO", false), equalTo("bar")));
+    }
 }