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33 Cards in this Set
- Front
- Back
What must you do to instantiate writing to a file object?
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PrintWriter writer = new PrintWriter(new FileWriter("outfile.txt"));
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What must you do after writing to a file?
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writer.close();
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How must you declare that you might get an error related to reading and writing from files?
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throws IOException in method heading
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What must your code look like to read from a file?
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Scanner filescan = new Scanner(new FileReader('infile.txt"));
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How must you instantiate a Random object?
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Random random = new Random();
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What is the javadoc format?
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/**
Description @param @return */ |
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What happens when a primitive variable is passed to a method?
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CANNOT CHANGE THE CORRESPONDING VARIABLE IN MAIN FROM WITHIN THE METHOD
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What happens when an object reference is passed to a method?
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-parameter variable points to the original object
-changes made in the method are permanent |
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Instance methods are called with ______
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class object and may interact directly on instance data methods
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Static methods are called with ______
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the class name (does not need any instance methods to do its job because it is stand alone)
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The reference variable holds the ______, whereas the object holds ______
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memory location of the object; the actual data
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What methods does the Object class in Java contain?
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clone ()
toString () equals() |
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Array indices must start at __
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0
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We must declare a ___ to create
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size capacity
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______ tells us the declared size of an array
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.length
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How do you declare an array of ints carrying 20?
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int ra = new int[20];
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How do you access first index and set it to 23?
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ra[0] = 23;
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How do you initialize an array in one line?
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int hw[] = {45, 65, 32}
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int [][] ra (which one is columns and which rows?
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first is rows
second is columns |
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What does .length mean for two dimensional arrays?
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number of rows
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How efficient are the various sorting methods?
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Bubble sort: n^2
selection sort: n^2 merge sort: n log n |
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How efficient are the searching methods?
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Binary search: log n
linear search: n |
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What is method overloading?
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Same name. different parameters
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What is method overriding?
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Same name, Same parameters
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What does extends mean?
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subclass extends base class
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What does super mean?
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to call base class constructor or over-ridden method in base class
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What does instanceof mean?
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to see if an object belongs to a specific class
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What does protected mean?
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to give access to derived classes
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What does implements mean?
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to say a class will have a method definitions to support an interface
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What is the method that is in the Comparable class?
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int compareTo(Object o)
returns negative int if < param, positive int if > param, 0 if the same |
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How should you display error messages?
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System.err.print()
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If operation throws an exception that is not caught, what will happen?
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program will stop and printStackTrace
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What are unchecked Exception classes?
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RuntimeException
NullPointerException InputMismatchException |