Example for Builder Pattern

BuilderTest.java

package net.lamtran.rxjava2;

import org.junit.Test;

import static org.hamcrest.MatcherAssert.assertThat;
import static org.hamcrest.core.IsEqual.equalTo;
import static org.junit.Assert.assertNotNull;

/**
 * Created by lam on 9/23/16.
 */

public class BuilderTest {

  @Test
  public void testRequestPaymentBuilder() throws Exception {
    RequestPayment request = new RequestPayment.Builder()
        .setBillId("bill_id")
        .setServiceId("service_id")
        .setProviderId("provider_id")
        .setCustomerCode("customer_code")
        .build();
    assertNotNull(request);
    assertThat(request.getBillId(), equalTo("bill_id"));
    assertThat(request.getServiceId(), equalTo("service_id"));
    assertThat(request.getProviderId(), equalTo("provider_id"));
    assertThat(request.getCustomerCode(), equalTo("customer_code"));
  }
}

RequestPayment.java

package net.lamtran.rxjava2;

/**
 * Created by lam on 9/23/16.
 */

public class RequestPayment {

  private final String mBillId;

  private final String mCustomerCode;

  private final String mProviderId;

  private final String mServiceId;

  RequestPayment(Builder builder) {
    mBillId = builder.billId;
    mCustomerCode = builder.customerCode;
    mProviderId = builder.providerId;
    mServiceId = builder.serviceId;
  }

  public String getBillId() {
    return mBillId;
  }

  public String getCustomerCode() {
    return mCustomerCode;
  }

  public String getProviderId() {
    return mProviderId;
  }

  public String getServiceId() {
    return mServiceId;
  }

  public static final class Builder {

    private String billId;

    private String customerCode;

    private String providerId;

    private String serviceId;

    public RequestPayment build() {
      return new RequestPayment(this);
    }

    public Builder setBillId(String billId) {
      this.billId = billId;
      return this;
    }

    public Builder setCustomerCode(String customerCode) {
      this.customerCode = customerCode;
      return this;
    }

    public Builder setProviderId(String providerId) {
      this.providerId = providerId;
      return this;
    }

    public Builder setServiceId(String serviceId) {
      this.serviceId = serviceId;
      return this;
    }
  }
}