ARROW-6472: [Java] ValueVector#accept may has potential cast exception

Related to [ARROW-6472](https://issues.apache.org/jira/browse/ARROW-6472).

If we use visitor API this way:
>RangeEqualsVisitor visitor = new RangeEqualsVisitor(vector1, vector2);
vector3.accept(visitor, range)

if vector1/vector2 are say, StructVector}}s and vector3 is an {{IntVector - things can go bad. we'll use the compareBaseFixedWidthVectors() and do wrong type-casts for vector1/vector2.

Discussions see:
apache#5195 (comment)
https://issues.apache.org/jira/browse/ARROW-6472

Closes apache#5483 from tianchen92/ARROW-6472 and squashes the following commits:

3d3d295 <tianchen> add test
12e4aa2 <tianchen> ARROW-6472:  ValueVector#accept may has potential cast exception

Authored-by: tianchen <[email protected]>
Signed-off-by: Pindikura Ravindra <[email protected]>

java/vector/src/main/java/org/apache/arrow/vector/compare/ApproxEqualsVisitor.java

@@ -69,8 +69,14 @@ public void setDoubleDiffFunction(DiffFunctionDouble doubleDiffFunction) {
   @Override
   public Boolean visit(BaseFixedWidthVector left, Range range) {
     if (left instanceof Float4Vector) {
+      if (!validate(left)) {
+        return false;
+      }
       return float4ApproxEquals(range);
     } else if (left instanceof Float8Vector) {
+      if (!validate(left)) {
+        return false;
+      }
       return float8ApproxEquals(range);
     } else {
       return super.visit(left, range);

java/vector/src/main/java/org/apache/arrow/vector/compare/RangeEqualsVisitor.java

@@ -58,7 +58,11 @@ public RangeEqualsVisitor(ValueVector left, ValueVector right, boolean isTypeChe
     Preconditions.checkArgument(right != null,
         "right vector cannot be null");
 
-    // types cannot change for a visitor instance. so, the check is done only once.
+    // type usually checks only once unless the left vector is changed.
+    checkType();
+  }
+
+  private void checkType() {
     if (!isTypeCheckNeeded) {
       typeCompareResult = true;
     } else if (left == right) {
@@ -68,6 +72,17 @@ public RangeEqualsVisitor(ValueVector left, ValueVector right, boolean isTypeChe
     }
   }
 
+  /**
+   * Validate the passed left vector, if it is changed, reset and check type.
+   */
+  protected boolean validate(ValueVector left) {
+    if (left != this.left) {
+      this.left = left;
+      checkType();
+    }
+    return typeCompareResult;
+  }
+
   /**
    * Constructs a new instance.
    *
@@ -79,7 +94,7 @@ public RangeEqualsVisitor(ValueVector left, ValueVector right) {
   }
 
   /**
-   * Check range equals without passing IN param in VectorVisitor.
+   * Check range equals.
    */
   public boolean rangeEquals(Range range) {
     if (!typeCompareResult) {
@@ -107,42 +122,59 @@ public ValueVector getRight() {
     return right;
   }
 
-  public boolean isTypeCheckNeeded() {
-    return isTypeCheckNeeded;
-  }
-
   @Override
   public Boolean visit(BaseFixedWidthVector left, Range range) {
+    if (!validate(left)) {
+      return false;
+    }
     return compareBaseFixedWidthVectors(range);
   }
 
   @Override
   public Boolean visit(BaseVariableWidthVector left, Range range) {
+    if (!validate(left)) {
+      return false;
+    }
     return compareBaseVariableWidthVectors(range);
   }
 
   @Override
   public Boolean visit(ListVector left, Range range) {
+    if (!validate(left)) {
+      return false;
+    }
     return compareListVectors(range);
   }
 
   @Override
   public Boolean visit(FixedSizeListVector left, Range range) {
+    if (!validate(left)) {
+      return false;
+    }
     return compareFixedSizeListVectors(range);
   }
 
   @Override
   public Boolean visit(NonNullableStructVector left, Range range) {
+    if (!validate(left)) {
+      return false;
+    }
     return compareStructVectors(range);
   }
 
   @Override
   public Boolean visit(UnionVector left, Range range) {
+    if (!validate(left)) {
+      return false;
+    }
     return compareUnionVectors(range);
   }
 
   @Override
   public Boolean visit(ZeroVector left, Range range) {
+    if (!validate(left)) {
+      return false;
+    }
     return true;
   }
 

java/vector/src/test/java/org/apache/arrow/vector/compare/TestRangeEqualsVisitor.java

@@ -86,6 +86,31 @@ public void testIntVectorEqualsWithNull() {
     }
   }
 
+  @Test
+  public void testEqualsWithTypeChange() {
+    try (final IntVector vector1 = new IntVector("intVector1", allocator);
+         final IntVector vector2 = new IntVector("intVector2", allocator);
+         final BigIntVector vector3 = new BigIntVector("bigIntVector", allocator)) {
+
+      vector1.allocateNew(2);
+      vector1.setValueCount(2);
+      vector2.allocateNew(2);
+      vector2.setValueCount(2);
+
+      vector1.setSafe(0, 1);
+      vector1.setSafe(1, 2);
+
+      vector2.setSafe(0, 1);
+      vector2.setSafe(1, 2);
+
+      RangeEqualsVisitor visitor = new RangeEqualsVisitor(vector1, vector2);
+      Range range = new Range(0, 0, 2);
+      assertTrue(vector1.accept(visitor, range));
+      // visitor left vector changed, will reset and check type again
+      assertFalse(vector3.accept(visitor, range));
+    }
+  }
+
   @Test
   public void testBaseFixedWidthVectorRangeEqual() {
     try (final IntVector vector1 = new IntVector("int", allocator);