ObjectInstantiationInEqualsHashCode

Reports construction of (temporary) new objects inside equals(), hashCode(), compareTo(), and Comparator.compare() methods.

Besides constructor invocations, new objects can also be created by autoboxing or iterator creation inside a foreach statement. This can cause performance problems, for example, when objects are added to a Set or Map, where these methods will be called often.

The inspection will not report when the objects are created in a throw or assert statement.

Example:

class Person {
    private String name;
    private int age;

    public boolean equals(Object o) {
      return Arrays.equals(new Object[] {name, age}, new Object[] {((Foo)o).name, ((Foo)o).age});
    }

    public int hashCode() {
      return (name + age).hashCode();
    }
  }

In this example, two additional arrays are created inside equals(), usages of age field require boxing, and name + age implicitly creates a new string.