What restrictions are placed on the location of a package statement within a source code file?

A package statement must appear as the first line in a source code file (excluding blank lines and comments).


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What is the difference between preemptive scheduling and time slicing?

Under preemptive scheduling, the highest priority task executes until it enters the waiting or dead states or a higher priority task comes into existence. Under time slicing, a task executes for a predefined slice of time and then reenters the pool of ready tasks. The scheduler then determines which task should execute next, based on priority and other factors.


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What are wrapped classes?

Wrapped classes are classes that allow primitive types to be accessed as objects.


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How many bits are used to represent Unicode, ASCII, UTF-16, and UTF-8 characters?

Unicode requires 16 bits and ASCII require 7 bits. Although the ASCII character set uses only 7 bits, it is usually represented as 8 bits. UTF-8 represents characters using 8, 16, and 18 bit patterns. UTF-16 uses 16-bit and larger bit patterns.


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What modifiers may be used with an inner class that is a member of an outer class?

A (non-local) inner class may be declared as public, protected, private, static, final, or abstract.


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Why do threads block on I/O?

Threads block on i/o (that is enters the waiting state) so that other threads may execute while the i/o Operation is performed.


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How do I convert a numeric IP address like 192.18.97.39 into a hostname like java.sun.com? (Networking)

String hostname = InetAddress.getByName("192.18.97.39").getHostName();


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