SCJP Cheat Sheet 2026

The 30 highest-yield SCJP facts, distilled from real exam questions. Print it, save it as a PDF, or study it here — free, no sign-up.

1. Which Java feature allows a class to inherit behavior from multiple sources without multiple inheritance of classes? → Interfaces with default methods
2. Which of the following is true about abstract classes in Java? → They can contain both abstract and concrete methods
3. Which Java I/O class should be used to write primitive data types (int, double, boolean) to a stream? → DataOutputStream
4. Which of the following methods can modify a String object, s? → none of the above will change s
5. In Java, can a single `catch` block catch multiple exception types? → Yes, using a pipe (|) separator since Java 7 (multi-catch)
6. The following class(es)' methods can be used to create directories: → File
7. Which interface should be implemented to allow objects to be sorted using `Arrays.sort()` without a Comparator? → Comparable
8. Which of the following is NOT part of the Java Collections Framework hierarchy? → Array
9. What will be the result of 7 % 3 in Java? → 1
10. Which of the following is a correct way to create a new thread in Java? → Extend Thread class or implement Runnable interface
11. Which of the following correctly describes method overloading in Java? → Same method name, different parameter list in the same class
12. What is the effect of calling `System.gc()`? → It is a request to the JVM to run garbage collection; the JVM may ignore it
13. Which collection class is best suited for implementing a LIFO (Last-In-First-Out) stack in modern Java? → java.util.ArrayDeque
14. What is an enum in Java? → A special class that represents a group of named constants
15. What is the default value of an instance variable of type boolean in Java? → false
16. In Java, which method pair is used for inter-thread communication? → notify() and wait()
17. Which of the following initialization strategies for the array "dayhigh" with seven values is correct? → int dayhigh[] = { 24, 23, 24, 25, 25, 23, 21 };
18. Which of the following statements about a two-dimensional array of numbers is legal? → int[]a[] = new int[5][5];
19. What does the `PriorityQueue` class use to determine the order of elements? → Natural ordering or a Comparator
20. What does the `Collections.sort()` method require from the objects it sorts? → Objects must implement Comparable
21. Which of the following exceptions is an unchecked exception? → NullPointerException
22. Which concurrent collection class is designed for high-concurrency scenarios and partitions its data to reduce lock contention? → ConcurrentHashMap
23. What is encapsulation in Java? → Hiding implementation by restricting direct access to fields and exposing via methods
24. Can a non-static inner class declare static members? → Yes, but only static final constant fields
25. What is the effect of marking a class member as `private`? → Accessible only within the declaring class
26. What happens when a subclass constructor does not explicitly call a superclass constructor? → The default no-arg superclass constructor is called implicitly
27. Given `TreeSet ts = new TreeSet<>(); ts.add(5); ts.add(1); ts.add(3);`, what does `ts.first()` return? → 1
28. In Java, which method retrieves an enum constant by its name string? → EnumType.valueOf(name)
29. Which of the following best describes the order in which a component is redrawn as a result of method calls? → invoke repaint() which invokes update(), which in turn invokes paint()
30. Which statement about the `finalize()` method is TRUE? → It is called by the garbage collector at most once per object