OCP-1Z0-819

OCP Oracle Certified Professional Java SE 11 Developer practices notes.

Symbol names, math expressions and statements

Keywords

Packages

package is optional.

Access modifiers

Class

Types

Variables

Operators

Flow Control

Arrays

Collections

Objects in memory

• Variables are stored in the Stack.
• Objects are stored in the Heap.
• Object references are pointers and variables, they are stored in the Stack.

Exceptions

Logging API

• module: requires java.logging
• import java.util.logging.*
• Levels from bottom to top:
  • Severe
  • Warning
  • Info
  • Config
  • Fine
  • Finer
  • Finest

Assertions

assert <boolean expression>;
assert <boolean expression> : <error text expression> ;

Lambdas

Streams

IO

Threads

Modularity

Annotations

• @FunctionalInterface enforce the definition of a functional interface: only one abstract method
• @Override verify that a method actually overrides a parent operation
• @Deprecation
• @SuppressWarnings unchecked or deprecation

JDBC

public class Example {
  public static void main(String[] args) {
    String url = "jdbc:derby:localhost:1527:productDB";
    String username = "pm";
    String pwd = "not-a-password";
    BigDecimal price = BigDecimal.valueOf(10.3);
    String productQuery = "select id, name from products where price > ?";
    try (Connection c = DriverManager.getConnection(url, username, pwd);
         PreparedStatement s = c.prepareStatement(productQuery);
         s.setBigDecimal(1, price);
         ResultSet rs = s.executeQuery();         
    ) {

      while (rs.next()){
          int id = rs.getInt(1);
      }

    } catch (SQLException e) {
      String state = e.getSQLState();
      int code = e.getErrorCode();
    }
  }
}