What's this CLASSPATH thing?

Question

I am really new to Java. I'm at the very start of a book titled "Teach Yourself Java" and I'm trying execute the first example. This is it:
class Example1 {
public static void main(String args[]) {
System.out.println("This is the output from Example1");
I downloaded and installed Java SE into:
C:\Program Files\Java\jdk1.6.0_11
I defined folder C:\Java Applications and put my first file in there titled Example1.java. I'm Windows XP PRO BTW.
At first it wouldn't compile because it couldn't find command javac. Based an another thread here I went into Start | Control Panel | System | Advanced | Environment Variables and updated variable PATH by adding to the end of it ;C:\Program Files\Java\jdk1.6.0_11\bin. It now compiles. But when I try to execute it with command
java Example1.java I get error Exception in thread "main" java.lang.NoClassDefFoundError.
I've read a dozen threads on this problem and most say something about adding a set CLASSPATH or a -cp command between command java and Example1.java. I've tried about everyone of the solutions but no luck. Where exactly is the main class it can't find? What do I need for it to find it when I execute it?

Answer 1

winke04 wrote:
I am really new to Java. I'm at the very start of a book titled "Teach Yourself Java" and I'm trying execute the first example. This is it:
class Example1 {
public static void main(String args[]) {
System.out.println("This is the output from Example1");
I downloaded and installed Java SE into:
C:\Program Files\Java\jdk1.6.0_11
I defined folder C:\Java Applications and put my first file in there titled Example1.java. I'm Windows XP PRO BTW.
At first it wouldn't compile because it couldn't find command javac. Based an another thread here I went into Start | Control Panel | System | Advanced | Environment Variables and updated variable PATH by adding to the end of it ;C:\Program Files\Java\jdk1.6.0_11\bin. It now compiles. But when I try to execute it with command
java Example1.java I get error Exception in thread "main" java.lang.NoClassDefFoundError.
I've read a dozen threads on this problem and most say something about adding a set CLASSPATH or a -cp command between command java and Example1.java. I've tried about everyone of the solutions but no luck. Where exactly is the main class it can't find? What do I need for it to find it when I execute it?(Probable) solution:
// to compile:
javac Example1.java
// to run:
java -cp . Example1Don't forget the DOT after "-cp"!
Explanation: [http://en.wikipedia.org/wiki/Classpath_(Java)]