Intro to XPath

Helpful XPath syntax reference from W3

Sample code based loosely on this Java2S example:

import javax.xml.xpath.XPath;
import javax.xml.xpath.XPathConstants;
import javax.xml.xpath.XPathExpressionException;
import javax.xml.xpath.XPathFactory;

import org.w3c.dom.NodeList;
import org.xml.sax.InputSource;

public class XMLParserAlpha
{
private static final String SOURCE = "C:/someFolder/xmlFile.xml";
private static final String EXPR = "*";

public static void main(String[] args)
{
XPath xpath = XPathFactory.newInstance().newXPath();
String xpathExpression = EXPR;
InputSource inputSource = new InputSource(SOURCE);

NodeList nodes = null;
int j = -1;
try
{
nodes = (NodeList) xpath.evaluate(xpathExpression, inputSource, XPathConstants.NODESET);
// NODESET maps to interface org.w3c.dom.NodeList
j = nodes.getLength();

for (int i = 0; i < j; i++) { System.out.println(nodes.item(i).getTextContent()); } } catch (XPathExpressionException e) { e.printStackTrace(); } } }

Other values of EXPR and what they're good for:
/Report/PublicationMetadata/DescriptiveMetadata/Title/@* - All attribute values of the title element (but not the attribute names)

TODO: FINISH POST

Intro to working with XML using Java

Rob Lybarger wrote a great intro article about this, the link skips to page two of five: Working with XML and Java

Syntactic sugar

Syntactic sugar on Wikipedia

"[Syntactic sugar is] syntax designed to make things easier to read or to express, while alternative ways of expressing them exist. It makes the language 'sweeter' for humans to use...." -Wikipedia

Array index behavior in Java

int indexFor1D = 3;
int indexFor2D = 1;
int [] array1D = { 5, 6, 7, 8, 9 };
int [][] array2D = {{1, 2}, {3, 4, 5}, {6, 7, 8, 9}};

System.out.println("From 2D: " + array2D[indexFor2D++][indexFor2D++]);
System.out.println("indexFor2D: " + indexFor2D);

array1D[indexFor1D++] = indexFor1D;
System.out.println("indexFor1D: " + indexFor1D);
System.out.print("New 1D: ");
for(int tmp : array1D)
System.out.print(tmp);

produces output

From 2D: 5
indexFor2D: 3
indexFor1D: 4
New 1D: 56749

Nerd Sniping or: Finally Always Wins, Unless You Crash The Machine Beforehand.

try {
return true;
} finally {
return false;
}

http://stackoverflow.com/questions/1995113/strangest-language-feature/2005435#2005435

Rules for bits in Java

All integer literals are, by default, ints in Java. All floating point literals are, by default, doubles. If a value larger than allowed is put into a given primitive type, the leftmost bits are discarded. So,

char c = (char) 65656; // Binary 00000000000000010000000001111000
byte i = (byte) 130; // Binary 00000000000000000000000010000010

A char is 16 bits, so it is set to 0000000001111000, which equals 1111000, which is 120, which in turn is the character 'z'; a byte is eight bits, so it is set to 10000010. Since the first bit is a sign bit, this actually equals -126. (By two's complement, 10000010 = -(01111101 + 1) = -(01111110) = -126.)

Division by zero in Java

Incredibly, the following code will compile without any problems:


int x = 7/0;
System.out.println(x);

int y = 0;
int z = 7/y;
System.out.println(z);


When the inevitable runtime error occurs, it appears as an ArithmeticException; there is no such thing as DivideByZeroException.