Add a DoubleArray example.

src/test/java/net/openhft/lang/values/DoubleArray.java

@@ -9,15 +9,16 @@ import net.openhft.lang.model.Copyable;
  * Created by peter.lawrey on 23/04/2015.
  */
 public class DoubleArray implements Byteable, Copyable<DoubleArray> {
-    private static int LENGTH = 0; // assume a 32-bit size.
-    private static int CAPACITY = LENGTH + 4; // assume a 32-bit size.
-    private static int BASE = CAPACITY + 4;
+    private static int CAPACITY = 0; // assume a 32-bit size.
+    private static int LENGTH = CAPACITY + 4; // assume a 32-bit size.
+    private static int BASE = LENGTH + 4;
 
     private Bytes bytes;
     private long offset;
 
     public DoubleArray(int capacity) {
         bytes = DirectStore.allocate(BASE + capacity * 8L).bytes();
+        bytes.writeInt(CAPACITY, capacity);
         offset = 0;
     }
 

src/test/java/net/openhft/lang/values/DoubleArrayTest.java

@@ -0,0 +1,48 @@
+package net.openhft.lang.values;
+
+import org.junit.Test;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.fail;
+
+public class DoubleArrayTest {
+
+    @Test
+    public void testSetData() {
+        DoubleArray da = new DoubleArray(64);
+        da.setData(new double[]{1, 2, 3, 4, 5, 6, 7, 8});
+        assertEquals(8, da.length());
+        for (int i = 0; i < da.length(); i++)
+            assertEquals(i + 1.0, da.getDataAt(i), 0.0);
+        da.addData(9);
+        da.addData(10);
+        double[] ds = new double[64];
+        int len = da.getDataUsing(ds);
+        assertEquals(10, len);
+        for (int i = 0; i < len; i++)
+            assertEquals(i + 1.0, ds[i], 0.0);
+
+        for (int i = 0; i < 64; i++)
+            ds[i] = i * 1.01;
+        da.setData(ds);
+        assertEquals(64, da.length());
+        for (int i = 0; i < da.length(); i++)
+            assertEquals(i * 1.01, da.getDataAt(i), 0.0);
+
+        double[] ds2 = new double[65];
+        assertEquals(64, da.getDataUsing(ds2));
+        for (int i = 0; i < 64; i++) {
+            assertEquals(i * 1.01, da.getDataAt(i), 0.0);
+            assertEquals(i * 1.01, ds2[i], 0.0);
+        }
+
+        try {
+            da.setData(ds2);
+            fail();
+        } catch (IllegalArgumentException expected) {
+            // expected
+        }
+        // free the memory.
+        da.bytes().release();
+    }
+}