What would you use to compare two String variables - the operator == or the method equals()?

Java Interview Questions and Answers (part 1)

(Continued from previous question...)

30. What would you use to compare two String variables - the operator == or the method equals()?

I'd use the method equals() to compare the values of the Strings and the == to check if two variables point at the same instance of a String object.

(Continued on next question...)

Other Interview Questions

• What's Java?
• What does a well-written OO program look like?
• Can you have virtual functions in Java?
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• How could Java classes direct program messages to the system console, but error messages, say to a file?
• What's the difference between an interface and an abstract class?
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• What do you understand by Synchronization?
• What is Collection API?
• Is Iterator a Class or Interface? What is its use?
• What is similarities/difference between an Abstract class and Interface?
• How to define an Abstract class?
• How to define an Interface?
• If a class is located in a package, what do you need to change in the OS environment to be able to use it?
• How many methods in the Serializable interface?
• How many methods in the Externalizable interface?
• What is the difference between Serializalble and Externalizable interface?
• What is a transient variable?
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• How are Observer and Observable used?
• What is synchronization and why is it important?
• What are synchronized methods and synchronized statements?
• What are three ways in which a thread can enter the waiting state?
• Can a lock be acquired on a class?
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• What is thread?
• What is multi-threading?
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• How to create a thread in a program?
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• What invokes a thread's run() method?
• What is the purpose of the wait(), notify(), and notifyAll() methods?
• What are the high-level thread states?
• What is the difference between yielding and sleeping?
• What happens when a thread cannot acquire a lock on an object?
• What is the difference between Process and Thread?
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• What modifiers may be used with an inner class that is a member of an outer class?
• If a method is declared as protected, where may the method be accessed?
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• What are wrapped classes?
• Does garbage collection guarantee that a program will not run out of memory?
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• Name Component subclasses that support painting?
• What is a native method?
• How can you write a loop indefinitely?
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• What is the purpose of finalization?
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• Is the numeric promotion available in other plantform?
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• What is the Properties class?
• What is the purpose of the Runtime class?
• What is the purpose of the System class?
• What is the purpose of the finally clause of a try-catch-finally statement?
• What is the Locale class?
• What is an abstract method?
• What is the difference between interface and abstract class?
• What is a static method?
• What is a protected method?
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• What are peerless components?
• What is the difference between the Font and FontMetrics classes?
• What is the difference between the Reader/Writer class hierarchy and the InputStream/OutputStream class hierarchy?
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• What is the difference between throw and throws keywords?
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• What is the Map interface?
• Does a class inherit the constructors of its superclass?
• Name primitive Java types.
• Which class should you use to obtain design information about an object?
• How can a GUI component handle its own events?
• How are the elements of a GridBagLayout organized?
• What advantage do Java's layout managers provide over traditional windowing systems?
• What are the problems faced by Java programmers who don't use layout managers?
• What is the difference between static and non-static variables?
• What is the difference between the paint() and repaint() methods?
• What is the purpose of the File class?
• Why would you use a synchronized block vs. synchronized method?
• What restrictions are placed on method overriding?
• What is casting?
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• What is the Set interface?
• How can you force garbage collection?
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• What is the difference between the File and RandomAccessFile classes?
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• What is Serialization and deserialization?
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• What is polymorphism?
• What is design by contract?
• What are use cases?
• What is scalability and performance?
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