[calcite] 04/05: Remove ArrayList allocation from Mappings#bijection, and add helpful message in case NPE is thrown

[vl...@apache.org]

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vladimirsitnikov pushed a commit to branch master
in repository https://gitbox.apache.org/repos/asf/calcite.git

commit fb2a02fb78f4e5b9b887645651b4b285ed68dacd
Author: Vladimir Sitnikov <si...@gmail.com>
AuthorDate: Fri Sep 4 23:39:27 2020 +0300

    Remove ArrayList allocation from Mappings#bijection, and add helpful message in case NPE is thrown
    
    bijection requires all indices from [0..targets.size()-1) to be mapped
    to non-null, and NPE was thrown if that is not the case.
    
    The change adds extra message, so it is easier to see what aas the mapping.
---
 .../main/java/org/apache/calcite/util/mapping/Mappings.java    | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/core/src/main/java/org/apache/calcite/util/mapping/Mappings.java b/core/src/main/java/org/apache/calcite/util/mapping/Mappings.java
index 88d2c7e..269c6cd 100644
--- a/core/src/main/java/org/apache/calcite/util/mapping/Mappings.java
+++ b/core/src/main/java/org/apache/calcite/util/mapping/Mappings.java
@@ -426,11 +426,15 @@ public abstract class Mappings {
    *
    * <p>Throws if sources and targets are not one to one. */
   public static Mapping bijection(Map<Integer, Integer> targets) {
-    final List<Integer> targetList = new ArrayList<>();
+    int[] ints = new int[targets.size()];
     for (int i = 0; i < targets.size(); i++) {
-      targetList.add(targets.get(i));
+      Integer value = targets.get(i);
+      if (value == null) {
+        throw new NullPointerException("Index " + i + " is not mapped in " + targets);
+      }
+      ints[i] = value;
     }
-    return new Permutation(Ints.toArray(targetList));
+    return new Permutation(ints);
   }
 
   /**