1. Set environment variable JAVA_HOME of JDK location and add path %JAVA_HOME%\bin
2. Compile and execute .java with extra jar

javac -cp .;h:\app\lib\mysql-connector-java-5.1.41-bin.jar Test.java
java -cp .;h:\app\lib\mysql-connector-java-5.1.41-bin.jar Test

BigInteger[] currentKey = new BigInteger[7];
System.arraycopy(w, k * 7, currentKey, 0, 7);

ObjectType@Address

Directed: |E| = |V|^2
Undirected: |E| = |V|*(|V|-1)/2 + |V|
Equal matrix: G(i,j) = G(j,i)

For both directed and undirected:  

• Speace Complexity  
  • Adjacency Matrix O(V^2)
  • Adjacency List O(V+E)
  • Which one is better for sparse?
• How expensive it is to find (u, v) belongs to E?
  • Adjacency Matrix O(1)
  • Adjacency List O(degree(u)) (O(1) to find node and dig in)
    • Dense worst: O(V)
    • Sparse: O(1)

For undirected:

• How expensive it is to compute the degree of a node?
  • Adjacency Matrix O(V)
  • Adjacency List O(degree(u))

For directed:

• How expensive it is to compute the out degree of a node?
  • Adjacency Matrix O(V)
  • Adjacency List O(degree(u))
• How expensive it is to compute the in degree of a node?
  • Adjacency Matrix O(V)
  • Adjacency List O(V+E)

A fixed set of constants, such as months, states, and cards:

pubic class Card {
  private enum Suit {SPADE, HEART, DIAMOND, CLUB;}
  public static void main(String[] args) {
    System.out.println(Suit.CLUB); // Show "CLUB"
  } 
}
// Or declare here

(enum types must not be local)

public class News {
  public static void main(String[] args) {
    System.out.println(NewsFeed.SITE1.getUrl());
  }
}

enum NewsFeed {
  SITE1("http://www.test1.com"),
  SITE2("http://www.test2.com"),
  SITE3("http://www.test3.com"); // notice: "," and ";"
  
  private String url; 
  
  private NewsFeed(String url) {
    this.url = url;  // "this" could be "SITE1", "SITE2", or "SITE3" 
  }
  public String getUrl() { // url getter. If url is public then we don't need it
    return this.url;
  }
}

1. The order of methods doesn't matter.
2. The order of variables matter.

//error: cannot find symbol
int sum = 0;
int a = 5;
sum = a + b;
int b = 6;
System.out.println(sum);

1. Final class cannot be extended
2. Final methods cannot be overridden
3. Final variable cannot be re-assigned