SYSVEDA Information Technology Java Developer Interview Questions and Answers

In Java, == compares memory addresses while .equals() compares the actual content of objects.

• == compares memory addresses of objects, while .equals() compares the actual content of objects.

• == is used to compare primitive data types, while .equals() is used to compare objects.

• Example: String str1 = new String("hello"); String str2 = new String("hello"); str1 == str2 will be false, but str1.equals(str2) will be true.

In Java, == compares object references, while .equals() compares object values.

• Use == to compare if two object references point to the same memory location.

• Use .equals() to compare if two objects have the same values.

• Example: String str1 = new String("hello"); String str2 = new String("hello"); str1 == str2 will be false, but str1.equals(str2) will be true.

The volatile keyword in Java is used to indicate that a variable's value will be modified by different threads.

• Ensures visibility of changes made by one thread to other threads

• Prevents compiler optimizations that could reorder instructions

• Useful for variables accessed by multiple threads without synchronization

• Example: volatile boolean flag = true;

JAVA stands for Java Virtual Machine

• JAVA stands for Java Virtual Machine

• It is a programming language that follows the principle of 'write once, run anywhere'

• Java code is compiled into bytecode which can run on any platform with Java Virtual Machine (JVM)

• Examples of Java applications include web applications, mobile apps, and enterprise software

D/W Hashmap and ConcurrentHashmap are both implementations of the Map interface in Java, with the latter being thread-safe.

• D/W Hashmap stands for 'Doubly-Linked Hashmap' and is a custom implementation of a hashmap in Java that maintains insertion order.

• ConcurrentHashmap is a thread-safe implementation of the Map interface in Java, allowing multiple threads to access and modify it concurrently without causing data corru

HashMap is not synchronized and not thread-safe, while ConcurrentHashMap is thread-safe and allows concurrent access.

• HashMap is not synchronized, so it is not safe to use in a multi-threaded environment without external synchronization.

• ConcurrentHashMap uses internal synchronization mechanisms to ensure thread safety, allowing multiple threads to access and modify it concurrently.

• ConcurrentHashMap is designed to handle...read more

In Java, == compares memory addresses while .equals() compares the actual content of objects.

• == is used to compare memory addresses of objects, while .equals() is used to compare the actual content of objects.

• == is used for primitive data types comparison, while .equals() is used for object comparison.

• Example: String str1 = new String("hello"); String str2 = new String("hello"); str1 == str2 will return false, but str1

The difference between == and equals() in Java for comparing object references and values.

• Use == to compare object references (memory location)

• Use equals() to compare object values

• Example: String str1 = new String("hello"); String str2 = new String("hello"); str1 == str2 will be false, but str1.equals(str2) will be true

Java stands for Just Another Virtual Machine

• Java stands for Just Another Virtual Machine

• It is a high-level programming language developed by Sun Microsystems

• Java code is compiled into bytecode that runs on any Java Virtual Machine (JVM)