1Z0-829 Utilizing Java Object-Oriented Approach Practice Question

Answer analysis

Option-by-option breakdown

For each option: why learners choose it and why it is or isn't the right answer here.

• ✓

  Override equals() with @Override, check identity (==), check null/class, cast, compare fields, override hashCode() with @Override, use Objects.hash() with same fields

  Why this is correct

  This order ensures the equals() and hashCode() contract: reflexive, symmetric, transitive, consistent; and that equal objects have equal hash codes.

• ✗

  Override hashCode() with @Override and Objects.hash(), then override equals() with @Override, check identity, cast, compare fields (skip type/null check)

  Why it's wrong here

  This order may compile but violates the contract because skipping the type/null check in equals() can cause ClassCastException or inconsistent results. Also, defining hashCode() before equals() risks inconsistency if fields are not finalized.

• ✗

  Override equals() with @Override, check identity, cast directly compare fields, override hashCode() with @Override using random values

  Why it's wrong here

  Missing the type/null check can lead to ClassCastException. Using random values for hashCode() breaks the contract: equal objects would have different hash codes, causing issues in hash-based collections.

• ✗

  Override equals() with @Override, check identity, check type, override hashCode() with @Override and Objects.hash(), then cast and compare fields

  Why it's wrong here

  The casting and field comparison must occur inside equals() before the method ends. Placing hashCode() in between is syntactically invalid and conceptually wrong—it breaks the structure of the equals() method.

Go deeper

Related to this question