Merge pull request functionaljava#10 from magro/string-functions

mperry · mperry · commit 899f7797b751 · 2014-06-02T20:21:13.000+10:00
Add isNullOrEmpty, isNullOrBlank and isNotNullOrBlank to Strings.
diff --git a/core/src/main/java/fj/function/Strings.java b/core/src/main/java/fj/function/Strings.java
@@ -2,7 +2,10 @@
 
 import fj.F;
 import fj.F2;
+import fj.data.Stream;
 import static fj.Function.curry;
+import static fj.function.Booleans.not;
+import static fj.function.Characters.isWhitespace;
 
 /**
  * Curried string functions.
@@ -14,8 +17,41 @@ private Strings() {
     throw new UnsupportedOperationException();
   }
 
+  /**
+   * This function checks if a given String contains any non-whitespace character
+   * (according to {@link Character#isWhitespace(char)}) and if it's also not
+   * <code>null</code> and not empty ("").
+   * 
+   * @see #isNullOrBlank
+   * @see Character#isWhitespace(char)
+   * @see Characters#isWhitespace
+   */
+  public static final F<String, Boolean> isNotNullOrBlank = new F<String, Boolean>() {
+    @Override
+    public Boolean f(final String a) {
+      return isNotNullOrEmpty.f(a) && Stream.fromString(a).find(not(isWhitespace)).isSome();
+    }
+  };
+
+  /**
+   * This function checks if a given String is whitespace (according to {@link Character#isWhitespace(char)}),
+   * empty ("") or <code>null</code>.
+   * 
+   * @see #isNotNullOrBlank
+   * @see Character#isWhitespace(char)
+   * @see Characters#isWhitespace
+   */
+  public static final F<String, Boolean> isNullOrBlank = new F<String, Boolean>() {
+    @Override
+    public Boolean f(final String a) {
+      return isNullOrEmpty.f(a) || Stream.fromString(a).find(not(isWhitespace)).isNone();
+    }
+  };
+
   /**
    * This function checks if a given String is neither <code>null</code> nor empty.
+   * 
+   * @see #isNullOrEmpty
    */
   public static final F<String, Boolean> isNotNullOrEmpty = new F<String, Boolean>() {
     @Override
@@ -24,6 +60,18 @@ public Boolean f(final String a) {
     }
   };
 
+  /**
+   * This function checks if a given String is <code>null</code> or empty ({@link String#isEmpty()}).
+   * 
+   * @see #isNotNullOrEmpty
+   */
+  public static final F<String, Boolean> isNullOrEmpty = new F<String, Boolean>() {
+    @Override
+    public Boolean f(final String a) {
+      return a == null || a.length() == 0;
+    }
+  };
+
   /**
    * A curried version of {@link String#isEmpty()}.
    */
