refactored ArraySequence.hashCode(), confirmed that the computed hash is...

refactored ArraySequence.hashCode(), confirmed that the computed hash is unchanged. #51

src/main/java/gov/usgs/earthquake/nshmp/data/ArrayXySequence.java

@@ -6,6 +6,7 @@ import static gov.usgs.earthquake.nshmp.Text.NEWLINE;
 
 import java.util.Arrays;
 import java.util.Iterator;
+import java.util.Objects;
 import java.util.stream.DoubleStream;
 
 import com.google.common.base.Joiner;
@@ -98,11 +99,7 @@ class ArrayXySequence implements XySequence {
 
   @Override
   public final int hashCode() {
-    final int prime = 31;
-    int result = 1;
-    result = prime * result + Arrays.hashCode(xs);
-    result = prime * result + Arrays.hashCode(ys);
-    return result;
+    return Objects.hash(Arrays.hashCode(xs), Arrays.hashCode(ys));
   }
 
   @Override