Block.java

import java.util.ArrayList;
import java.util.Calendar;

public class Block implements java.io.Serializable{
	private static final long serialVersionUID = 1L;
	private int difficultyLevel = 22;
	private ArrayList<String> transactions = new ArrayList<String>();
	private long timestamp;
	private String previousBlockHashID;
	private int nonce = 0;
	private String hashID;
	
	public Block(String previousBlockHashID, int difficultyLevel) {
		this.previousBlockHashID = previousBlockHashID;
		this.timestamp = UtilityMethods.getTimeStamp();
		this.difficultyLevel = difficultyLevel;
	}
	protected String computeHashID() {
		StringBuilder sb = new StringBuilder();
		sb.append(this.previousBlockHashID + Long.toHexString(this.timestamp));
		for(String t : transactions) {
			sb.append(t);
		}
		sb.append(Integer.toHexString(this.difficultyLevel) + nonce);
		byte[] b = UtilityMethods.messageDigestSHA256_toBytes(sb.toString());
		return UtilityMethods.toBinaryString(b);
	}
	
	public void addTransaction(String s) {
		this.transactions.add(s);
	}
	public String getHashID() {
		return this.hashID;
	}
	public int getNonce() {
		return this.nonce;
	}
	public long getTimeStamp() {
		return this.timestamp;
	}
	public String getPreviousBlockHashID() {
		return this.previousBlockHashID;
	}
	protected boolean mineTheBlock() {
		this.hashID = this.computeHashID();
		while(!UtilityMethods.hashMeetsDifficultyLevel(this.hashID, this.difficultyLevel)) {
			this.nonce++;
			this.hashID = this.computeHashID();
		}
		return true;
	}
	public int getDifficultyLevel() {
		return this.difficultyLevel;
	}

}