@@ -80,7 +80,7 @@ public class SortField implements Serializable {
    * @return true if this order satisfies the given order
    */
   public boolean satisfies(SortField other) {
-    if (this == other) {
+    if (Objects.equals(this, other)) {
       return true;
     } else if (sourceId != other.sourceId || direction != other.direction || nullOrder != other.nullOrder) {
       return false;
/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */

package org.apache.iceberg;

import java.io.Serializable;
import java.util.Objects;
import org.apache.iceberg.transforms.Transform;

/**
 * A field in a {@link SortOrder}.
 */
public class SortField implements Serializable {

  private final Transform<?, ?> transform;
  private final int sourceId;
  private final SortDirection direction;
  private final NullOrder nullOrder;

  SortField(Transform<?, ?> transform, int sourceId, SortDirection direction, NullOrder nullOrder) {
    this.transform = transform;
    this.sourceId = sourceId;
    this.direction = direction;
    this.nullOrder = nullOrder;
  }

  /**
   * Returns the transform used to produce sort values from source values.
   *
   * @param <S> the Java type of values transformed by the transform function
   * @param <T> the Java type of values returned by the transform function
   * @return the transform
   */
  @SuppressWarnings("unchecked")
  public <S, T> Transform<S, T> transform() {
    return (Transform<S, T>) transform;
  }

  /**
   * Returns the field id of the source field in the {@link SortOrder sort order's} table schema
   */
  public int sourceId() {
    return sourceId;
  }

  /**
   * Returns the sort direction
   */
  public SortDirection direction() {
    return direction;
  }

  /**
   * Returns the null order
   */
  public NullOrder nullOrder() {
    return nullOrder;
  }

  /**
   * Checks whether this field's order satisfies another field's order.
   *
   * @param other another sort field
   * @return true if this order satisfies the given order
   */
  public boolean satisfies(SortField other) {
    if (this == other) {
      return true;
    } else if (sourceId != other.sourceId || direction != other.direction || nullOrder != other.nullOrder) {
      return false;
    }

    return transform.satisfiesOrderOf(other.transform);
  }

  @Override
  public String toString() {
    return transform + "(" + sourceId + ") " + direction + " " + nullOrder;
  }

  @Override
  public boolean equals(Object other) {
    if (this == other) {
      return true;
    } else if (other == null || getClass() != other.getClass()) {
      return false;
    }

    SortField that = (SortField) other;
    return transform.equals(that.transform) &&
        sourceId == that.sourceId &&
        direction == that.direction &&
        nullOrder == that.nullOrder;
  }

  @Override
  public int hashCode() {
    return Objects.hash(transform, sourceId, direction, nullOrder);
  }
}

even though using Ref equlity is correct here, it just takes the reader much longer to verify whether it's the intention or not than just using `equals()` here