question regarding Structural and Behavioural Design Patterns in Java.

Below is my code, and I would like to apply thru the practical application the following design patterns/strategies: Adapter, Observer and Proxy.

package com.algonquin.loggy;

import java.util.Date; import java.util.Random; import java.util.UUID;

public abstract class Log implements Annotable { private String name; private String description; private Date date; private UUID uuid; private String code; private File attachment;

public File getAttachment() { return attachment; }

public void setAttachment(File attachment) { this.attachment = attachment; }

public void create() { System.out.println("Log record for " + uuid + " has been created"); }

public void read() { System.out.println("Log " + uuid + " name:" + name + ", description: " + description + " created on " + date); }

public void update(String name, String description) { System.out.println("Log record for " + uuid + " has been updated"); this.name = name; this.description = description; }

public void delete() { System.out.println("Log record for " + uuid + " has been deleted"); }

public String getName() { return name; }

public void setName(String name) { this.name = name; }

public String getDescription() { return description; }

public void setDescription(String description) { this.description = description; }

public UUID getUuid() { return uuid; }

public void setUuid(UUID uuid) { this.uuid = uuid; }

public Date getDate() { return date; }

public void setDate(Date date) { this.date = date; } private Log(LogBuilder builder) { //builder implementation

this.name = builder.name;

this.description = builder.description;

this.date = builder.date;

this.uuid = builder.uuid;

this.code = builder.code;

this.attachment = builder.attachment;

} public static class LogBuilder {

private String name;

private String description;

private Date date;

private UUID uuid;

private String code;

private File attachment;

public LogBuilder(String name, String description, Date date, UUID uuid, String code, File attachment) {

super();

this.name = name;

this.description = description;

this.date = date;

this.uuid = uuid;

this.code = code;

this.attachment = attachment;

}

public LogBuilder LogBuilder() {

return null;

}

}

public Log() { this.name = null; this.description = null; this.date = null; this.uuid = null; this.code = null; }

public Log(String name) { this(name, ""); }

public Log(String name, String description) { this(name, description, new Date()); }

public Log(String name, String description, Date date) { this.name = name; this.description = description; this.date = date; this.uuid = UUID.randomUUID(); Singleton s=Singleton.getInstance(); this.code = s.shortCode(); }

public String toString() { String out = code + ":" + name + ":" + description + ":" + date; if (this.attachment != null) { out += " with attachment " + this.attachment.getName(); } return out; }

@Override public void attachFile(String name, String type, String content, Long size) throws Exception { if (!isValidContentType(type)) { System.out.println("ContentType " + type + " can not be attached"); throw new Exception("ContentType " + type + " can not be attached"); } }

@Override public boolean isValidContentType(String type) { return false; }

private String shortCode() { return randomChars(3) + "-" + randomChars(3) + "-" + randomChars(3); }

private String randomChars(int n) { String randomchars = ""; String chars = "abcdefghijklmnopqrstuvwxyz1234567890"; Random rnd = new Random(); for (int i = 0; i < n; i++) { randomchars += chars.charAt(rnd.nextInt(chars.length())); } return randomchars; } }

------

package com.algonquin.loggy;

import java.util.ArrayList;

public class Main {

public static void main(String[] args) {

Log log = null;

Log.LogBuilder logbuilder = new Log.LogBuilder(null, null, null, null, null, null).LogBuilder();

System.out.println("Log builder config::"+logbuilder);

ArrayList aList = new ArrayList<>();

aList.add(new Factory("first log", "Monday May 3, I had to wake up early",

"image.tif", "TIF", "******", Long.valueOf(1024)));

aList.add(new Factory("fourth log", "And even later, I need to have lunch",

"eating.png", "PNG", "******", Long.valueOf(1024)));

aList.add(new Factory("first log", "Monday May 4, I had to wake up early",

"image.png", "PNG", "******", Long.valueOf(1024)));

aList.add(new Factory("second log", "Few minutes later, I had my first cup of coffee",

"coffee.png", "PNG", "******", Long.valueOf(1024)));

aList.add(new Factory("third log", "Few minutes later, I am going for a ride",

"biking1.mp4", "MP4", "******", Long.valueOf(1024)));

aList.add(new Factory("fourth log", "And even later, I need to have lunch",

"recipie.txt", "TXT", "******", Long.valueOf(1024)));

for (int ctr = 0; ctr < aList.size(); ++ctr) {

try {

mockLog(aList.get(ctr).getLog(), aList.get(ctr).getFile());

}

catch (Exception e) {

System.out.println("Exception: " + e.getMessage() + " ");

// e.printStackTrace();

}

}

}

private static void mockLog(Log log, File file) throws Exception {

System.out.println(">>> New log (" + log.toString() + ")");

log.setAttachment(file);

log.create();

System.out.println(" ");

}

}

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package com.algonquin.loggy;

public class File implements Processable {

private String name;

private String type;

private String content;

private Long size;

public File() {

}

public File(String name, String type, String content, Long size) {

this.name = name;

this.type = type;

this.content = content;

this.size = size;

}

public String getContent() {

return content;

}

public void setContent(String content) {

this.content = content;

}

public String getName() {

return name;

}

public void setName(String name) {

this.name = name;

}

public String getType() {

return type;

}

public void setType(String type) {

this.type = type;

}

public Long getSize() {

return size;

}

public void setSize(Long size) {

this.size = size;

}

@Override

public void postProcess() {

System.out.println("Default post processing");

}

}

-------------------

package com.algonquin.loggy;

public interface Annotable {

public void attachFile(String name, String type, String content, Long size) throws Exception;

public boolean isValidContentType(String contentType);

}

----------------

/** * */ package com.algonquin.loggy;

public class TextFile extends File {

/** * */ public TextFile() { }

/** * @param name * @param type * @param content * @param size */ public TextFile(String name, String type, String content, Long size) { super(name, type, content, size); }

/** * */ @Override public void postProcess() { super.postProcess(); // trigger translation System.out.println("This text file is going to be translated"); }

}