100 lines
3.2 KiB
Plaintext
100 lines
3.2 KiB
Plaintext
This file contains a walkthrough on how to use important tools in Java. These
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include Vectors, Enumerations and StringTokenizers. All of these classes are
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located in the package java.util
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VECTORS
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===============================================================================
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In order to use the Vector class, you need to import java.util.Vector.
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Look in the Java API to see a list of all the methods that can be used with
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Vectors. The great thing about Vectors is that they are dynamic like
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Linked Lists, but they give instantaneous access to elements like arrays.
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So lets say we had a small java class that utilized Vectors. We want to add
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words when a person says them into the Vector - as long as the word is not in
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the Vector already. When they are done speaking, we want to print out all of
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the words that they said.
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import java.util.Vector;
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public class SaveWords
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{
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public SaveWords(){
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Vector v = new Vector();
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String word = "";
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while((word = WordISay()) != null) // as long as I say a word
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{
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if(!(v.contains(word))) // check to see if in Vector
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{
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// if not add it
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v.add(word)
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}
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} // end while
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// loop through the vector (notice the size() method)
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for(int i = 0; i<v.size(); i++)
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{
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// use v.elementAt to get a specific element without
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// removing it.
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System.out.println(v.elementAt(i));
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}
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}
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}
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This is a simple walkthrough. Other useful and important methods deal with
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removing an object and getting the index of an object. Look in the API for
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these methods. Check out the elements method as well. This method returns
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an Enumeration of all the elements in the Vector (see below).
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ENUMERATION
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============================================================================
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The important methods for Enumeration are
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hasMoreElements and nextElement.
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hasMoreElements returns true if there are more elements while nextElement will
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return the next Object of the Enumeration. Example of use...
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Enumeration e.....
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while(e.hasMoreElements()){
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// do something with e.nextElement()
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// remember that this is an Object and may need to be casted into the
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// appropriate Object
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} // end while
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STRING TOKENIZER
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=============================================================================
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The StringTokenizer class is very similar to the Enumeration class with respect
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to the methods that are able to be called. The small difference is that the
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actual methods are called hasMoreTokens() and nextToken(). The nextToken method
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returns a String as opposed to an Object. The StringTokenizer class does
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exactly what it says...it tokenizes (breaks up) a string. The default delimiter
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is white space. Thus if a StringTokenizer was declared as
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StringTokenizer st = new StringTokenizer("How Are you doing?");
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then the code
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while(st.hasMoreTokens()){
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System.out.println(st.nextToken());
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}
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would produce the following output
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How
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Are
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you
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doing?
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if instead the StringTokenizer was declared to delimit with respect to o's
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StringTokenizer st = new StringTokenizer("How Are you doing?", "o");
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then the output would be...
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H
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w Are y
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u d
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ing? |