INFORMATION NOW

Implicit or Automatic Type Casting

• In this, smaller data type is converted to bigger data type which is also known as widening.
• There is no data loss chance.
• It is done by compiler therefore it is known as automatic type casting.
• Example: byte b=10; int x=b; Here byte type is converted to int type.

Explicit Type Casting

• In this, bigger data type is converted to smaller data type which is also known as narrowing.
• There is data loss chance.
• It is done by the user with the help of type cast operator i.e. ( ).
• Example: int x=10; byte b=(byte)x; Here int type is converted to byte type.

Type Promotion in Java

• Converting smaller data type to bigger data type is known as type promotion.
• Only promotion is allowed, demotion is not allowed.

Type Promotion Chart

• This chart tells us about the flow of converting one smaller data type to another bigger data type.
• Double can’t be converted to any data type.

• JVM is responsible for taking .class file and converting that .class file in machine code instructions that can be executed by microprocessor.
• It’s not a machine, it’s a program.
• JVM verifies the code before execution (Sandbox Security).
• JVM is platform dependent and it is heart of Java language.

There are four phases of JVM

• Load Code
• Verify Code
• Execute Code
• Provide Runtime Environment

Overview of Java virtual machine (JVM) architecture and structure

Use of Super Keyword in Java

• Access parent class instance variable.

• Invoke parent class method.

• Invoke parent class constructor.

class parent
{
                int x=20;              
                parent()
                {
                                System.out.println("Parent");
                }

                void show()
                {
                                System.out.println("Parent Show");
                }
}

class child extends parent
{
                int x=30;

                child()
                {
                                super();                                //invoke parent constructor
                }

                void show()
                {
                                System.out.println("Child Show");
                }

                void display()
                {
                                System.out.println(x);                   //print child x
                                System.out.println(super.x);      //print parent x

                                show();                                //invoke child show()
                                super.show();   //invoke parent show()
                }

                public static void main(String...s)
                {
                                child c=new child();
                                c.display();
                }
}                  

• Here both the classes have variable x and method show(). To access variable of child class we simply write x and to access variable of parent class we write super.x.

• Similarly, to invoke method of child we simple write show() and to invoke method of parent we write super.show(). In this way super is also used to remove the problem of method overriding.

• super() must be first line of the constructor. In above example we have written super() in first line of child class constructor to call parent class constructor.

• Super can’t be used in static method.

• By default super is first line of constructor. Super keyword and this keyword can’t be used together in constructor.

package moftobean.netapp;
import java.io.BufferedReader;
import java.io.File;
import java.io.FileOutputStream;
import java.io.FileReader;
import java.util.HashMap;
import java.util.StringTokenizer;

public class JavaBeanMOF {
 /**
  * @param args
  */
 public static void main(String[] args) {
 try {
  int i;
  FileOutputStream fout = null;
  File f2;
  File f = new File("D:/SVNSTSWorkspace/NetApp Bean Generator/src/moftobean/netapp/ontap_battery.mof");
  // folder name that the bean files will reside in a package
  String namespace = "netapp"; 
  FileReader fin = new FileReader(f);
  BufferedReader bin = new BufferedReader(fin);
  String line = null;
  HashMap <string string=""> map = new HashMap<string string="">();
  while((line = bin.readLine()) != null) { 
   if(line.trim().startsWith("class")) {
    if(map.get(line) == null) {
     map.put(line, line);
     String cname = line.split(" ")[1];
     String name = "D:/SVNSTSWorkspace/NetApp Bean Generator/src/moftobean/netapp/" + cname + ".java";
     String packagePath = "package moftobean." + namespace + ";

";
     f2 = new File(name);
     fout = new FileOutputStream(f2);
     fout.write(packagePath.getBytes());
     i = 0;
     if(line.contains(":")) {
      //separate’s tokens based on space and colon
      StringTokenizer st = new StringTokenizer(line,"[ :]");  
      String[] tokenlist = new String[st.countTokens()];
      while (st.hasMoreTokens()) {
       tokenlist[i] = st.nextToken();
       i++;
      } 
      String str1;
      if(tokenlist[1].startsWith("ONTAP_") || tokenlist[3].startsWith("CIM_")) {
      str1 = "public "+tokenlist[0]+" "+tokenlist[1]+" "+"extends"+" "+tokenlist[2]+" {";
      System.out.println(str1);
      fout.write((str1+"
").getBytes()); 
      }
     } 
    }
    
   }
   if(line.trim().endsWith(";") &amp;&amp; !line.trim().startsWith("}")) {
    String[] tokens = line.trim().split(" ");
    
    if(tokens.length == 2) {
     for(String token: tokens) {
      if(token.trim().equalsIgnoreCase("string")) {
       line = "String ";
      } else if(token.trim().equalsIgnoreCase("uint16")) {
       line = "UnsignedInteger16 " ;
      } 
      // continue if you have more variable types in MOF file
      
      if(token.trim().endsWith(";")) {
       line = line+token;
      }
     } 
    }
    System.out.println(line);
    fout.write((line + "
").getBytes());
   }
   if(line.trim().startsWith("}") &amp;&amp; line.trim().endsWith(";")) {
    System.out.println("}");
    fout.write(("}" + "
").getBytes());
   }

  }
  bin.close();
 } catch(Exception e) { e.printStackTrace(); }
 }
}

Output: Two Java files are generated with the respective names.

ONTAP_Battery.java

package moftobean.netapp;

public class ONTAP_Battery extends CIM_Battery {
String SystemCreationClassName;
String SystemName;
String CreationClassName;
String DeviceID;
String Description;
String ElementName;
UnsignedInteger16 BatteryStatus;
}

ONTAP_StorageSystemBattery.java 

package moftobean.netapp;

public class ONTAP_StorageSystemBattery extends CIM_SystemDevice {
      ONTAP_StorageSystem REF GroupComponent;
      ONTAP_Battery REF PartComponent;
}