JavaByExample.java

"two\nlines"
"\"This is in quotes\""

int d = 3, e, f = 5;
byte z = 22;
double pi = 3.14159;
char x = 'x';

z = (byte) f;

byte b = 42;
char c = 'a';
short s = 1024;
int i = 50000;
float f = 5.67f;
double d = .1234;

 // final is similar to const in C/C++/C#
    final   int   FILE_NEW = 1;


b = (byte) i;

int month_days[] = { 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 };

int twoD45[][]= new int[4][5];

int twoD[][] = new int[4][];
twoD[0] = new int[1];
twoD[1] = new int[2];
twoD[2] = new int[3];
twoD[3] = new int[4];

double m[][] = {
   { 0*0, 1*0, 2*0, 3*0 },
   { 0*1, 1*1, 2*1, 3*1 },
   { 0*2, 1*2, 2*2, 3*2 },
   { 0*3, 1*3, 2*3, 3*3 }
};

System.out.println("lengths are: " + month_days.length + " " + twoD45.length + " " + twoD.length);

if(i == 10) {
  if(j < 20) a = b;
  d++;
}
else if(i == 11) 
  i++;
else a = d;          // this else refers to if(i == 10)

  switch(i) {
    case 0:
      System.out.println("i is zero.");
      break;
    case 1:
      System.out.println("i is one.");
      break;
case 3:
case 4:
    default:
      System.out.println("i is greater than one.");
  }
}

  int n = 20;
  while(n > 10) {
    System.out.println("tick " + n);
    n--;
  }

do {
  System.out.println("tick " + n);
  n--;
} while(n > 0);

for(int a=1, int b=4; a<b; a++, b--) {
  System.out.println("a = " + a);
  System.out.println("b = " + b);
}

  for(int n=10; n>0; n--)
    System.out.print(n + " ");
    if(n == 6) break; // terminate loop 
    if(n%2 == 0) continue;
    System.out.println("");
}

  first: {
    second: {
      third: {
        System.out.println("Before the break.");
        if(t) break second; // break out of second block
        System.out.println("This won't execute");
      }
      System.out.println("This won't execute");
    }
    System.out.println("This is after second block.");
  }
}

// Demonstrating some String methods.
class StringDemo2 {
  public static void main1(String args[]) {
    String strOb1 = "First String";
    String strOb2 = "Second String";
    String strOb3 = strOb1;
    System.out.println("Length of strOb1: " +
                       strOb1.length());
    System.out.println("Char at index 3 in strOb1: " +
                       strOb1.charAt(3));

    if(strOb1.equals(strOb2))
      System.out.println("strOb1 == strOb2");
    else
      System.out.println("strOb1 != strOb2");
    if(strOb1.equals(strOb3))
      System.out.println("strOb1 == strOb3");
    else
      System.out.println("strOb1 != strOb3");
  }
public static void main2(String args[]) {
  String str[] = { "one", "two", "three" };
  for(int i=0; i<str.length; i++)
    System.out.println("str[" + i + "]: " +
                        str[i] + ". Length: " str[i].length());
}
}

class Box {
  double width;
  double height;
  double depth;

  // This is the constructor for Box.
  Box(double w, double h, double d) {
    width = w;
    height = h;
    depth = d;
  }
  // compute and return volume
  double volume() {
    return width * height * depth;
  }
protected void finalize( )
{
    System.out.println("finalized.");
}

}

// Here, Box is extended to include weight.
class BoxWeight extends Box {
  double weight; // weight of box
  // initialize width, height, and depth using super()
  BoxWeight(double w, double h, double d, double m) {
    super(w, h, d); // call superclass constructor
    weight = m;
  }
}

The subclass BoxWeight is used as a superclass to create the subclass called
Shipment. Shipment inherits all of the traits of BoxWeight and Box, and adds
a field called cost, which holds the cost of shipping such a parcel.


Box mybox; // declare reference to object
mybox = new Box(3, 6, 9); // allocate a Box object

When a simple type is passed to a method, it is done by use of
call-by-value. Objects are passed by use of call-by-reference.

public static int divide(int[] array, int index) {
  try {
    System.out.println("\nFirst try block in divide() entered");
    array[index + 2] = array[index]/array[index + 1];
    System.out.println("Code at end of first try block in divide()");
    return array[index + 2];
  } catch(Exception e) {
    System.err.println("Exception caught in divide()\n" +
                       "\nMessage in exception object:\n\t" +
                         e.getMessage());
    System.err.println("\nStack trace output:\n");
    e.printStackTrace();
  } finally {
    System.err.println("finally clause in divide()");
  }
  System.out.println("Executing code after try block in divide()");
  return array[index + 2];
}

// Display all command-line arguments.
class CommandLine {
  public static void main(String args[]) {
    for(int i=0; i<args.length; i++)
      System.out.println("args[" + i + "]: " +
                          args[i]);
  }
}