#Java

27 questions

• What is Java and what is "write once, run anywhere"?Java#languageJunior›
• What is the difference between JVM, JRE and JDK?Java#platformJunior›
• What are primitive types vs reference types in Java?Java#languageJunior›
• What are the four pillars of OOP?Java#oopJunior›
• How do classes, objects and constructors work?Java#oopJunior›
• What are Java's access modifiers?Java#languageJunior›
• Why are Java Strings immutable, and what is StringBuilder for?Java#languageJunior›
• How do arrays work in Java?Java#data-structuresJunior›
• What control-flow constructs does Java provide?Java#languageJunior›
• What do the static and final keywords mean?Java#languageJunior›
• What is the Java Collections Framework?Java#data-structuresMiddle›
• What is the difference between an interface and an abstract class?Java#oopMiddle›
• What are generics and why use them?Java#languageMiddle›
• Why must you override equals() and hashCode() together?Java#oopMiddle›
• What is the Stream API?Java#functionalMiddle›
• What are lambdas and functional interfaces?Java#functionalMiddle›
• What is Optional and how does it help with null?Java#languageMiddle›
• What is the difference between Comparable and Comparator?Java#data-structuresMiddle›
• How does multithreading work in Java?Java#concurrencySenior›
• How do you synchronize access to shared state?Java#concurrencySenior›
• How does JVM memory and garbage collection work?Java#performanceSenior›
• How do the Executor framework and CompletableFuture help with async work?Java#concurrencySenior›
• What are records and sealed classes?Java#languageSenior›
• What are reflection and annotations used for?Java#languageSenior›
• How do enums work in Java?Java#languageMiddle›
• What are the kinds of nested classes in Java?Java#oopMiddle›
• What is autoboxing and what are its pitfalls?Java#languageMiddle›