package com.google.sps.agents;
 
// Imports the Google Cloud client library
import com.google.cloud.dialogflow.v2.QueryInput;
import com.google.cloud.dialogflow.v2.QueryResult;
import com.google.protobuf.Struct;
import com.google.protobuf.Value;
import com.google.sps.data.Output;
import com.google.sps.agents.Agent;
import java.io.IOException;
import java.util.Map;
 
/**
 * Currency Agent
 */

public class Currency implements Agent {
  private final String intentName;
  private String currencyFrom;
  private String currencyTo;
  private Double amount;
  private String fulfillment = null;;
  private String diplay = null;
  private String redirect = null;

  public Currency(String intentName, Map<String, Value> parameters) {
	  this.intentName = intentName;
	  setParameters(parameters);
  }

  @Override 
  public void setParameters(Map<String, Value> parameters) {
	  currencyFrom = parameters.get("currency-from").getStringValue();
	  currencyTo = parameters.get("currency-to").getStringValue();
	  amount = parameters.get("amount").getNumberValue();

	  fulfillment = "Redirecting for conversion";
	  String baseURL = "http://www.google.com/search?q=";
	  String endURL = String.join("+", "Convert", String.valueOf(amount), currencyFrom, "to", currencyTo); 
	  redirect = baseURL + endURL;
  }

  @Override
  public String getOutput() {
	  return fulfillment;
  }

  @Override
  public String getDisplay() {
	  return display;
  }

  @Override
  public String getRedirect() {
	  return redirect;
  }
}

package com.google.sps.agents;
 
// Imports the Google Cloud client library
import com.google.cloud.dialogflow.v2.QueryInput;
import com.google.cloud.dialogflow.v2.QueryResult;
import com.google.protobuf.Struct;
import com.google.protobuf.Value;
import com.google.sps.data.Output;
import com.google.sps.agents.Agent;
import java.io.IOException;
import java.util.Map;
 
/**
 * Currency Agent
 */

public class Currency implements Agent {
  private final String intentName;
  private String currencyFrom;
  private String currencyTo;
  private Double amount;
  private String fulfillment = null;;
  private String diplay = null;
  private String redirect = null;

  public Currency(String intentName, Map<String, Value> parameters) {
    this.intentName = intentName;
    setParameters(parameters);
  }

  @Override 
  public void setParameters(Map<String, Value> parameters) {
    currencyFrom = parameters.get("currency-from").getStringValue();
    currencyTo = parameters.get("currency-to").getStringValue();
    amount = parameters.get("amount").getNumberValue();

    fulfillment = "Redirecting for conversion";
    String baseURL = "http://www.google.com/search?q=";
    String endURL = String.join("+", "Convert", String.valueOf(amount), currencyFrom, "to", currencyTo); 
    redirect = baseURL + endURL;
  }

  @Override
  public String getOutput() {
    return fulfillment;
  }

  @Override
  public String getDisplay() {
    return display;
  }

  @Override
  public String getRedirect() {
    return redirect;
  }
}

Update Currency.java