Assignment 1: ScroogeCoin

You will be responsible for creating a file called TxHandler.java that implements the following API:

public class TxHandler {

  /** Creates a public ledger whose current UTXOPool (collection of unspent
  * transaction outputs) is utxoPool. This should make a defensive copy of
  * utxoPool by using the UTXOPool(UTXOPool uPool) constructor.
  */
  public TxHandler (UTXOPool utxoPool);
  
  /** Returns true if
  * (1) all outputs claimed by tx are in the current UTXO pool,
  * (2) the signatures on each input of tx are valid,
  * (3) no UTXO is claimed multiple times by tx,
  * (4) all of tx’s output values are non-negative, and
  * (5) the sum of tx’s input values is greater than or equal to the sum of
  its output values; and false otherwise.
  */
  public boolean isValidTx (Transaction tx);
  
  /** Handles each epoch by receiving an unordered array of proposed
  * transactions, checking each transaction for correctness,
  * returning a mutually valid array of accepted transactions,
  * and updating the current UTXO pool as appropriate.
  */
  public Transaction[] handleTxs (Transaction[] possibleTxs);
}