From e6d4baa0b8d331a512e0925e4573766b32be73c3 Mon Sep 17 00:00:00 2001
From: Shekhar Gulati <shekhargulati84@gmail.com>
Date: Tue, 3 May 2016 20:05:19 +0530
Subject: [PATCH] Added `at` function

---
 README.md                            | 12 +++++++++++-
 src/main/java/strman/Strman.java     | 23 ++++++++++++++++++++++-
 src/test/java/strman/StrmanTest.java | 14 ++++++++++++--
 3 files changed, 45 insertions(+), 4 deletions(-)

diff --git a/README.md b/README.md
index c3b4214..94aa561 100644
--- a/README.md
+++ b/README.md
@@ -1,7 +1,7 @@
 strman-java
 ------
 
-A Java string manipulation library without any dependencies. It is inspired by [dleitee/strman](https://github.com/dleitee/strman).
+A Java 8 string manipulation library without any dependencies. It is inspired by [dleitee/strman](https://github.com/dleitee/strman).
 
 
 ## Available Functions
@@ -31,4 +31,14 @@ import static strman.Strman.appendArray;
 String title = "s";
 String result = appendArray(title, new String[]{"tr","m","an"});
 // result = "strman"
+```
+
+## at(value, index)
+
+Gets the character at index.
+
+```java
+import static strman.Strman.at;
+String result = at("foobar", 0);
+// result = "f"
 ```
\ No newline at end of file
diff --git a/src/main/java/strman/Strman.java b/src/main/java/strman/Strman.java
index 35291ca..2e3c762 100644
--- a/src/main/java/strman/Strman.java
+++ b/src/main/java/strman/Strman.java
@@ -1,5 +1,6 @@
 package strman;
 
+import java.util.Optional;
 import java.util.StringJoiner;
 
 /**
@@ -26,7 +27,7 @@ public interface Strman {
      * @param appends an array of strings to append
      * @return full String
      */
-    static String appendArray(String value, String[] appends) {
+    static String appendArray(final String value, final String[] appends) {
         if (value == null) {
             throw new IllegalArgumentException("'value' should be not null.");
         }
@@ -39,4 +40,24 @@ public interface Strman {
         }
         return value + joiner.toString();
     }
+
+    /**
+     * Get the character at index. This method will take care of negative indexes.
+     * The valid value of index is between -(length-1) to (length-1).
+     * For values which don't fall under this range Optional.empty will be returned.
+     *
+     * @param value input value
+     * @param index location
+     * @return an Optional String if found else empty
+     */
+    static Optional<String> at(final String value, int index) {
+        if (value == null || value.isEmpty()) {
+            return Optional.empty();
+        }
+        int length = value.length();
+        if (index < 0) {
+            index = length + index;
+        }
+        return (index < length && index >= 0) ? Optional.of(String.valueOf(value.charAt(index))) : Optional.empty();
+    }
 }
diff --git a/src/test/java/strman/StrmanTest.java b/src/test/java/strman/StrmanTest.java
index 60e52e2..431a2de 100644
--- a/src/test/java/strman/StrmanTest.java
+++ b/src/test/java/strman/StrmanTest.java
@@ -2,10 +2,13 @@ package strman;
 
 import org.junit.Test;
 
+import java.util.Optional;
+
 import static org.hamcrest.CoreMatchers.equalTo;
 import static org.junit.Assert.assertThat;
 import static strman.Strman.append;
 import static strman.Strman.appendArray;
+import static strman.Strman.at;
 
 public class StrmanTest {
 
@@ -28,11 +31,18 @@ public class StrmanTest {
         assertThat(appendArray("", new String[]{"foobar"}), equalTo("foobar"));
     }
 
-
     @Test(expected = IllegalArgumentException.class)
     public void appendArrayShouldThrowIllegalArgumentExceptionWhenValueIsNull() throws Exception {
         appendArray(null, new String[]{});
     }
 
-
+    @Test
+    public void shouldFindCharacterAtIndex() throws Exception {
+        assertThat(at("foobar", 0), equalTo(Optional.of("f")));
+        assertThat(at("foobar", 1), equalTo(Optional.of("o")));
+        assertThat(at("foobar", -1), equalTo(Optional.of("r")));
+        assertThat(at("foobar", -2), equalTo(Optional.of("a")));
+        assertThat(at("foobar", 10), equalTo(Optional.empty()));
+        assertThat(at("foobar", -10), equalTo(Optional.empty()));
+    }
 }
\ No newline at end of file