GuavaSelfEquals
An object is tested for equality to itself using Guava Libraries

Category
GUAVA
Severity
ERROR
Maturity

The problem

The arguments to this equal method are the same object, so it always returns true. Either change the arguments to point to different objects or substitute true.

Suppression

Suppress false positives by adding an @SuppressWarnings("GuavaSelfEquals") annotation to the enclosing element.


Positive examples

GuavaSelfEqualsPositiveCase.java

/*
 * Copyright 2011 Google Inc. All Rights Reserved.
 *
 * Licensed 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 com.google.errorprone.bugpatterns.testdata;

import com.google.common.base.Objects;

/**
 * @author alexeagle@google.com (Alex Eagle)
 */
public class GuavaSelfEqualsPositiveCase {
  private String field = "";

  @Override
  public boolean equals(Object o) {
    if (this == o) {
      return true;
    }
    if (o == null || getClass() != o.getClass()) {
      return false;
    }
    GuavaSelfEqualsPositiveCase other = (GuavaSelfEqualsPositiveCase) o;
    boolean retVal;
    // BUG: Diagnostic contains: Objects.equal(field, other.field)
    retVal = Objects.equal(field, field);
    // BUG: Diagnostic contains: Objects.equal(other.field, this.field)
    retVal &= Objects.equal(field, this.field);
    // BUG: Diagnostic contains: Objects.equal(this.field, other.field)
    retVal &= Objects.equal(this.field, field);
    // BUG: Diagnostic contains: Objects.equal(this.field, other.field)
    retVal &= Objects.equal(this.field, this.field);
    
    return retVal;
  }

  @Override
  public int hashCode() {
    return Objects.hashCode(field);
  }
  
  public static void test() {
    ForTesting tester = new ForTesting();
    // BUG: Diagnostic contains: Objects.equal(tester.testing.testing, tester.testing)
    Objects.equal(tester.testing.testing, tester.testing.testing);
  }
  
  private static class ForTesting {
    public ForTesting testing;
    public String string;
  }
}

Negative examples

GuavaSelfEqualsNegativeCases.java

/*
 * Copyright 2016 Google Inc. All Rights Reserved.
 *
 * Licensed 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 com.google.errorprone.bugpatterns.testdata;

import com.google.common.base.Objects;

/**
 * @author bhagwani@google.com (Sumit Bhagwani)
 */
public class GuavaSelfEqualsNegativeCases {
  private String field;

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

    GuavaSelfEqualsNegativeCases other = (GuavaSelfEqualsNegativeCases) o;
    return Objects.equal(field, other.field);
  }

  @Override
  public int hashCode() {
    return field != null ? field.hashCode() : 0;
  }
}