简单电话通讯录

Question

我刚开始使用Java编程，为了帮助我学习，我创建了一个简单的电话通讯录。代码按预期运行，但如果更高级的程序员认为我应该以不同的方式运行，我会对此感兴趣。

import com.mongodb.MongoClient;
import com.mongodb.MongoException;
import com.mongodb.DB;
import com.mongodb.DBCollection;
import com.mongodb.BasicDBObject;
import com.mongodb.DBCursor;

import java.net.UnknownHostException;
import java.util.Scanner;

import org.bson.types.ObjectId;

public class MongodbPhonebook {
    public static void main(String[] args) {
        boolean boolContinue = true;
        String stringCommand;
        Scanner input = new Scanner(System.in);

        try {
            MongoClient mongoClient = new MongoClient();
            DB db = mongoClient.getDB( "myphonelist" );
            DBCollection coll = db.getCollection("myphonelist");



            do {
                System.out.println("Enter command (add, find, show, quit): ");
                stringCommand = input.nextLine();
                if(stringCommand.equals("quit")){
                    boolContinue = false;
                }
                else if(stringCommand.equals("show")){
                    displayAll(coll);
                }
                else if(stringCommand.equals("add")){
                    insertNumber(coll);
                }
                else if(stringCommand.equals("find")){
                    findNumber(coll);
                }
                else {
                    System.out.println("Unknown command!");
                }
            } while(boolContinue == true);
        }
        catch (UnknownHostException e) {
            e.printStackTrace();
        }
        catch (MongoException e) {
            e.printStackTrace();
        } 
    }

    public static void displayAll(DBCollection collDisplay) {
        DBCursor cursor = collDisplay.find();
        try {
            while(cursor.hasNext()) {
                System.out.println(cursor.next());
            }
        } finally {
            cursor.close();
        }    
        return;
    }

    public static void insertNumber (DBCollection collInsert) {
        Scanner input = new Scanner(System.in);
        ObjectId stringID;
        String stringName = "";
        String stringNumber = "";
        System.out.println("Enter name: ");
        stringName = input.nextLine();
        System.out.println("Enter number: ");
        stringNumber = input.nextLine();
        BasicDBObject doc = new BasicDBObject("name", stringName).
                append("number", stringNumber);
        collInsert.insert(doc);
        stringID = (ObjectId)doc.get( "_id" );
        System.out.println("Result: " + stringID.toString());
        return;
    }

    public static void findNumber (DBCollection collFind) {
        Scanner input = new Scanner(System.in);
        String stringName = "";
        System.out.println("Enter name: ");
        stringName = input.nextLine();
        BasicDBObject query = new BasicDBObject("name", stringName);

        DBCursor cursor = collFind.find();
        cursor = collFind.find(query);

        try {
            while(cursor.hasNext()) {
                System.out.println("found " + cursor.next());
            }
        } finally {
            cursor.close();
        }
    }
}

Answer 1

我不知道您使用的JDK是哪个版本，但是在Java 7中，他们在字符串变量上引入了switch语句，而不仅仅是整数。相反，您的代码可以这样读，以使其更具可读性。

do {
                System.out.println("Enter command (add, find, show, quit): ");
                stringCommand = input.nextLine();
                switch(stringCommand)
                {
                    case "quit":
                         boolContinue = false;
                         break;
                    case "show":
                         displayAll(coll);
                         break;
                    case "add":
                         insertNumber(coll);
                         break;
                    case "find":
                         findNumber(coll);
                         break;
                    default:
                         System.out.println("Unknown command!");
                         break;
                }
            } while(boolContinue);   // A boolean variable by itself can be used as an expression. The == true expression is redundant.