Constructor Overloading in Java
Fast recall
Quick revision
Core answer
this(...) chaining so one constructor delegates to another instead of duplicating code.Whether you understand overloaded constructors and how this() chaining avoids duplicated initialization.
Duplicating the same initialization logic across constructors instead of delegating with this().
Show this() must be the first statement and that chaining funnels all constructors through one 'primary' constructor that holds the validation.
Interview-ready guide
Interview answer
The way I'd describe it is one class with several front doors. Each constructor takes a different parameter list, so a caller can build a Product with just a name, or with a name and a price, and the compiler picks the right one at compile time from the arguments passed to new.
What actually matters is the shared setup. The tempting mistake is writing each constructor to set every field and run its own validation — three constructors, three copies of the same logic, which drift until one forgets a null check. The clean approach is `this(...)` chaining: the lighter constructors delegate to a fuller one, and all real assignment and validation live in a single primary constructor. The catch is that this(...) must be the very first statement, or it won't compile.
One boundary to round it off: constructors can be overloaded but never overridden — they aren't inherited like methods. So overload freely for convenience, but funnel everything through one constructor, so there's exactly one place to maintain initialization.
Constructor Overloading in Java
Direct Answer
Constructor overloading is defining multiple constructors in the same class with different parameter lists, giving callers several ways to create an object. Like method overloading, the compiler picks the right one by the arguments at compile time. It's typically combined with this(...) chaining so one constructor delegates to another instead of duplicating code.
Common Mistakes & Pitfalls
- Copy-pasting initialization across constructors — duplicated field-setting and validation drift apart over time, so one constructor quietly skips a null check the others enforce.
- Putting code before
this(...)— the delegation call must be the first statement, so any line ahead of it is a compile error. - Trying to override a constructor — constructors can be overloaded but never overridden; they aren't inherited, so
@Overrideon one won't compile. - Distinguishing constructors only by parameter names — the compiler resolves by type, count, and order, so
Product(String a)andProduct(String b)are the same signature and can't coexist.
Check your understanding
Answer these without looking back at the article.
- What is the difference between constructor overloading and method overloading?
- What is constructor chaining in Java?
- Can constructors be overridden in Java?
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