Java Core Classes and Threads

(2) - This is a Java keyword (3) - This is a Java keyword (1) - Is incorrect because although it is a method of Thread/Runnable it is not a keyword (4) - This is not a Java keyword the keyword is implements

However A, B and C are all wrong. Each of these would result in a narrowing conversion. Whereas we want a widening conversion, therefore the only correct answer is D. Don't be put off by the long cast, this applies only to the variable x and not the rest of the expression. It is the variable y (of type double) that forces the widening conversion todouble. Java's widening conversions are:

• From a byte to a short, an int, a long, a float, or a double.
• From a short, an int, a long, a float, or a double.
• From a char to an int, a long, a float, or a double.
• From an int to a long, a float, or a double.
• From a long to a float, or a double.
• From a float to a double.

Option C is suitable to start a thread.

In Java, string literals are preferred and most commonly used to create string objects directly, utilizing string pooling efficiently. While the new keyword creates a new object in the heap explicitly, string literal assignment is the standard idiomatic practice.

Option D is correct. Garbage collection takes place after the method has returned its reference to the object. The method returns to line 6, there is no reference to store the return value. so garbage collection takes place after line 6. Option A is wrong. Because the reference to obj1 is stored in obj2[0]. The Object obj1still exists on the heap and can be accessed by an active thread through the reference stored in obj2[0]. Option B is wrong. Because it is only one of the references to the object obj1, the other reference is maintained in obj2[0]. Option C is wrong. The garbage collector will not be called here because a reference to the object is being maintained and returned in obj2[0].

The void keyword in Java (and C/C++) indicates that a method returns no value. It specifies the absence of a return type, meaning the method performs its action but doesn't produce any result that can be assigned to a variable.

The init() method is the first lifecycle method called when an applet is loaded. It initializes the applet's state, sets up components, and prepares the applet for execution. The start() method comes after init() and is called to begin the applet's active execution.

The applet lifecycle has four main methods: init() (called once when loaded), start() (called to begin execution), stop() (called when the applet should pause), and destroy() (called when the applet is being removed). The paint() method is for graphics, not a lifecycle method. Option D correctly lists the three core lifecycle methods.

As explained, all of the methods are defined in the Input Stream class.So this is the correct choice.

This is correct answer because as I explained all of the given methods are defined in the OutputStream class.

As I explained all of the methods are defined in the Reader class.So this is the correct choice.

This is the correct answer. There is no Subclass named charWriter. The correct name is CharArrayWriter which is used for writing to a char array.So this is the correct answer according to the question.

There is no subclass of Reader class named InputReader. The correct name is InputStreamReader used for reading a character stream.So this is the correct answer according to the question.

As I explained that all of the given methods are defined in the File class.So this is the correct answer.

As I explained both the classes in option 2 & 3 are the only subclasses of InputStream class.So this is the correct answer.