Error: Could not find or load main class hello in java code example

Example 1: eclipse Error: Could not find or load main class main java.lang.ClassNotFoundException

// Run configurations -> Run -> Run configurations
// In the Classpath tab select "Advanced"
// Add where Eclipse usually put the *.class for the projects, which is (usually) "bin".

Example 2: could not load main class java

// after compiling
$ javac Main.java
// instead of
$ java Main.class
// try running
$ java Main