JAVA

The package keyword specifies the Java package in which the classes declared in a Java source file reside. Examples package com.mycompany; public class MyClass { }

null is a Java reserved word representing no value. Examples Integer i; i = null; String s; if (s != null) { <statements> }

The new keyword is used to create a new instance of a class. Examples String sName = new String(); Float fVal = new Float(0.15);

The native keyword may be applied to a method to indicate that the method is implemented in a language other then Java. Examples native String getProcessorType();

long is a Java primitive type. A long variable may store a 64−bit signed integer. Examples long number = 5; long anotherNumber = 34590L; long octalNumber = 0377; long hexNumber = 0xffl;

The interface keyword is used to declare a new Java interface, which is a collection of methods. Interfaces are a powerful feature of the Java language. Any class may declare that it implements one or more interfaces, meaining it implements all of the methods defined in those interfaces. Examples public interface IPolygon { public float getArea(); public int getNumberOfSides(); public int getCircumference(); }

int is a Java primitive type. A int variable may store a 32−bit integer value. Examples int number = 5; int octalNumber = 0377; int hexNumber = 0xff;

The instanceof keyword is used to determine the class of an object. Examples if (node instanceof TreeNode) { <statements> }

The import keyword makes one class or all classes in a package visible in the current Java source file. Imported classes can be referened without the use of fully−qualified class names. Examples import java.io.File; import java.net.*;

The implements keyword is used in a class declaration to indicate that the class being declared provides implementations for all methods declared in the interface whose name follows the implements keyword. Examples public class Truck implements IVehicle { }

The for keyword specifies a loop whose condition is checked before each iteration. Examples int i; for (i=0; i<max; i++) { <statements> }

float is a Java primitive type. A float variable may store a single−precision floating point value. Examples float ratio = .01; float diameter = 6.15; float height = 1.35E03; // 1.35 * 103 or 1350.0 float height = 1e−2; // 1.0 * 10−2 or 0.01

The finally keyword is used to define a block that is always executed in a try−catch−finally statement. A finally block typically contains cleanup code that recovers from partial execution of a try block. Examples try { <block that may throw exceptions> } catch (<java.lang.Exception or subclass> e) { <code to handle exception e> } finally { <statements that execute with or without exception> }

The false keyword represents one of the two legal values for a boolean variable. Examples boolean isComplete = false;

The extends keyword is used in a class or interface declaration to indicate that the class or interface being declared is a subclass of the class or interface whose name follows the extends keyword. Examples public class Rectangle extends Polygon { }

The else keyword is always used in association with the if keyword in an if−else statement. The else clause is optional and is executed if the if condition is false. Examples if (condition) { <statements> } else { <statements> }

double is a Java primitive type. A double variable may store a double−precision floating point value. Examples double ratio = .01; double diameter = 6.15; double height = 1.35E03; // 1.35 * 103 or 1350.0 double height = 1e−2; // 1.0 * 10−2 or 0.01

The do keyword specifies a loop whose condition is checked at the end of each iteration. Examples do { <statements> } while (!found);

The default keyword is used to label the default branch in a switch statement. Examples int arg = <some value>; switch (arg) { case 1: <statements> break; case 2: <statements> break; default: <statements> break; }

The continue keyword is used to skip to the next iteration of a for, while, or do loop. Examples for (i=0; i<max; i++) { <statements> if (<done with this iteration>) { continue; } <statements> }