super Keyword in Java — Uses and Rules

Direct Answer

super refers to the parent class of the current object. It has three uses: super() calls the parent class constructor and must be the first statement in a subclass constructor; super.method() invokes the parent's version of an overridden method so you extend rather than replace its behavior; and super.field accesses a parent field when a subclass field hides it with the same name (rare in practice).

Code Example

class Account {
    protected double balance;

    // Parent constructor — requires a balance argument
    Account(double balance) {
        this.balance = balance;
    }

    String describe() {
        return "Balance: " + balance;
    }
}

class SavingsAccount extends Account {
    private double rate;

    SavingsAccount(double balance, double rate) {
        super(balance);   // super() MUST be first — passes balance to Account constructor
        // If you write ANY statement before super(), it is a compile error
        this.rate = rate; // only runs after parent is initialized
    }

    @Override
    String describe() {
        // super.describe() calls Account's version — extend, don't replace
        return super.describe() + ", rate: " + rate;
    }
}

public class SuperDemo {
    public static void main(String[] args) {
        SavingsAccount sa = new SavingsAccount(1000.0, 0.04);
        System.out.println(sa.describe());
        // Output: Balance: 1000.0, rate: 0.04
        // Without super.describe() we'd print only ", rate: 0.04"
    }
}

Common Mistakes & Pitfalls

• Assuming Java always inserts super() for you — it only inserts the no-arg call; if the parent has only parameterized constructors, your subclass won't compile until you write super(args) yourself.
• Overriding a framework method without calling super — skipping super.onCreate() or super.doFilter() silently drops the framework's own logic and produces bugs that are brutal to trace.
• Treating super.field as a normal tool — needing it means a subclass field is hiding a parent field of the same name, a design smell you should usually rename away.
• Trying to put code before super(...) — it must be the first statement, so you cannot validate arguments or log anything before the parent is constructed.