Top 10 Java confusion questions like this (very high interview probability)

Here are Top 10 Java Confusion Questions (very high interview probability) — explained clearly with examples 👇

1. == vs .equals()

String a = new String("Java");
String b = new String("Java");System.out.println(a == b);        // false ❌
System.out.println(a.equals(b));   // true ✅

👉 Key Point

• == → reference comparison
• .equals() → value comparison

2. final vs finally vs finalize()

• final → keyword (constant, no override)
• finally → block (always executes)
• finalize() → GC method (deprecated ❗)

3. ArrayList vs Array

• Array → fixed size
• ArrayList → dynamic

👉 Interview line:

“ArrayList resizes internally, array does not.”

4. HashMap vs Hashtable

• HashMap → not synchronized
• Hashtable → synchronized (legacy)

5. String vs StringBuilder vs StringBuffer

Type	Thread Safe	Mutable
String	❌	❌
StringBuilder	❌	✅
StringBuffer	✅	✅

6. Comparable vs Comparator

• Comparable → natural sorting (compareTo)
• Comparator → custom sorting (compare)

7. checked vs unchecked exception

• Checked → compile-time (IOException)
• Unchecked → runtime (NullPointerException)

8. overloading vs overriding

• Overloading → same method name, different params
• Overriding → same method in child class

9. this vs super

• this → current class
• super → parent class

10. length vs length() vs count()

Array  → length
String → length()
Stream → count()

Bonus (Very Tricky)

Arrays.asList() Trap

List<int[]> list = Arrays.asList(new int[]{1,2,3});

👉 Not List<Integer> ❗

💡 How to Use in Interview

If asked:
👉 “Tell some Java differences”

Pick any 2–3 and explain deeply instead of listing all.

🚀 Pro Tip

Focus most on:

• == vs equals
• ArrayList vs Array
• Comparable vs Comparator
• String vs StringBuilder

👉 These are asked almost every time