[Projeto final do curso]

OBS: Neste desafio tomei liberdade para escrever dois tipos de arquivos, um em formato JSON e outro em String mesmo. Json no arquiv nomeado "JsonJson" e o formato String no arquivo "JsontoString".

package challenge.services;

public class CepInfo {
    //variables
    private String cep;
    private String logradouro;
    private String bairro;
    private String localidade;
    private String uf;
    private String ddd;

    //getters and setters
    public String getCep() {
        return cep;
    }
    public void setCep(String cep) {
        this.cep = cep;
    }
    public String getLogradouro() {
        return logradouro;
    }
    public void setLogradouro(String logradouro) {
        this.logradouro = logradouro;
    }
    public String getBairro() {
        return bairro;
    }
    public void setBairro(String bairro) {
        this.bairro = bairro;
    }
    public String getLocalidade() {
        return localidade;
    }
    public void setLocalidade(String localidade) {
        this.localidade = localidade;
    }
    public String getUf() {
        return uf;
    }
    public void setUf(String uf) {
        this.uf = uf;
    }
    public String getDdd() {
        return ddd;
    }
    public void setDdd(String ddd) {
        this.ddd = ddd;
    }

    //constructor
    public CepInfo(String cep, String logradouro, String bairro, String localidade, String uf, String ddd) {
        this.cep = cep;
        this.logradouro = logradouro;
        this.bairro = bairro;
        this.localidade = localidade;
        this.uf = uf;
        this.ddd = ddd;
    }

    @Override
    public String toString() {
        return  "Cep: " +cep+ "\n"+
                "Logradouro: " +logradouro+ "\n"+
                "Bairro: " +bairro+ "\n"+
                "Localidade: " +localidade+ "\n"+
                "Uf: " +uf+ "\n"+
                "DDD: " +ddd+ "\n";
    }
}

package challenge.controller;
import challenge.services.CepInfo;
import com.google.gson.*;
import java.io.*;
import java.net.*;
import java.net.http.*;
import java.util.*;

public class ApiCep {
    Scanner scanner = new Scanner(System.in);
    private String search = scanner.nextLine();

    Gson gson = new GsonBuilder()
            .setPrettyPrinting()
            .create();

    public CepInfo apiCepInfo() throws IOException, InterruptedException{
        String url = "https://viacep.com.br/ws/" +search+ "/json/";
        HttpClient client = HttpClient.newHttpClient();
        HttpRequest request = HttpRequest.newBuilder()
                .uri(URI.create(url))
                .build();
        HttpResponse<String> response = client.send(request, HttpResponse.BodyHandlers.ofString());

        if (response.statusCode() == 400) {
            System.out.println("Error! Zip code not found!");
        }

        //writing in json
        System.out.println("Status code: " +response.statusCode());
        FileWriter fileJson = new FileWriter("JsonJson");
        fileJson.write(response.body());
        fileJson.close();
        System.out.println("File has been written successfully");

        //writing in different archive toString
        CepInfo cepInfo = gson.fromJson(response.body(), CepInfo.class);
        FileWriter fileToString = new FileWriter("JSONtoString");
        fileToString.write(cepInfo.toString());
        fileToString.close();
        System.out.println("File has been written successfully");

        return cepInfo;
    }
}

package challenge.main;
import challenge.controller.ApiCep;
import challenge.services.CepInfo;
import java.io.IOException;

public class Main {
    public static void main(String[] args) {
        System.out.println("Enter your cep to check: ");

        ApiCep apiCep = new ApiCep();
        try {
            CepInfo cepInfo = apiCep.apiCepInfo();
        } catch (IOException | InterruptedException e) {
            throw new RuntimeException(e);
        }
    }
}

Saída esperada:
Enter your cep to check: 
79072-460
Status code: 200
File has been written successfully
File has been written successfully