Java赋值不知道是什么错误

Question

the question is :

A fruit shop sells several types of fruits each day. Write a program that reads from user several lines of input.Each line includes a fruit's name,price per kilogram (as an integer), number of kilograms sold (as an integer).

the program should calculate and print the earned money of all fruits sold and fruit that achieved largest profit.

hint: -you could assume that user will insert valid data -user could stop the program via entering the word "stop" as a fruit's name.

Sample input and out put:

in each line, insert a fruit's name, price per kilogram, number of kilograms sold. To halt the program,insert "stop" as a fruit's name

---

banana 2 11 mango 3 8 peach 4 5

stop

---

the earned money of all fruits sold: 66 fruit that achieved the largest profit: mango

---

what i wrote now:

public static void main(String[] args) { 
// TODO code application logic here 
Scanner input = new Scanner (System.in); 
String fruitname= " "; 
String maxfruit = " "; 
int price = 0,number=0; 
int sum=0; 
int max=0; 


System.out.print("Fruit name, " + "price in killogram, number of killogram sold: "); 

while (!fruitname.equals("stop")) 
{ 
fruitname = input.next(); 
price = input.nextInt(); 
number = input.nextInt(); 
} 
if (fruitname.equals("stop")) 
{ 
sum = sum+(price*number); 

} 
if (max<(price*number)) 
{ 
max = price*number; 
maxfruit = fruitname; 
} 


System.out.println("the earned money of all fruits is " + sum); 
System.out.println("fruit that achieved the largest profit is "+ maxfruit); 
} 
} 

the program is not reading what i submit to it, don't know why and not giving me the sum and the max fruit.. what is the problem of what i wrote?

Answer 1

As you can see your reads happen in the while loop:

while (!fruitname.equals("stop")) 
{ 
    fruitname = input.next(); 
    price = input.nextInt(); 
    number = input.nextInt(); 
} 

Every time it loops - it overrides the values. Finally when you read stop and exit the loop - your fruitname is stop . So you need to fix your logic on how you would want to read in the input

Answer 2

Working variant:

public class FruitTest {

public static void main(String[] args) {
    Scanner input = new Scanner(System.in);


    System.out.print("Fruit name, " + "price in killogram, number of killogram sold: ");

    String text = input.nextLine();

    String[] words = text.split(" ");

    List<Fruit> fruits = parseInput(words);

    int sum = getSum(fruits);

    String popular = getPopularFruitName(fruits);

    System.out.println("Got fruits: " + fruits.toString());
    System.out.println("the earned money of all fruits is " + sum);
    System.out.println("fruit that achieved the largest profit is " + popular);
}

private static String getPopularFruitName(List<Fruit> fruits) {
    int max = 0;
    String name = null;

    for (Fruit fruit : fruits) {
        int checkVal = fruit.getPrice() * fruit.getAmount();
        if(checkVal > max) {
            max  = checkVal;
            name = fruit.getName();
        }
    }

    return name;
}

private static int getSum(List<Fruit> fruits) {
    int result = 0;
    for (Fruit fruit : fruits) {
        result += fruit.getPrice() * fruit.getAmount();
    }
    return result;
}

private static List<Fruit> parseInput(String[] words) {
    List<Fruit> result = new ArrayList<Fruit>();
    int element = 1;
    final int name = 1;
    final int price = 2;
    final int amount = 3;

    Fruit fruit = null;
    for (String word : words) {
        if (word.equals("stop") || word.isEmpty()) {
            break;
        }
        if(element > amount)
            element = name;

        switch (element) {
            case name:
                fruit = new Fruit(word);
                result.add(fruit);
                break;
            case price:
                if (fruit != null) {
                    fruit.setPrice(Integer.valueOf(word));
                }
                break;
            case amount:
                if(fruit != null) {
                    fruit.setAmount(Integer.valueOf(word));
                }
                break;
        }
        element++;
    }

    return result;
}

static class Fruit {
    String name;
    int price  = 0;
    int amount = 0;


    Fruit(String name) {
        this.name = name;
    }

    String getName() {
        return name;
    }

    int getPrice() {
        return price;
    }

    void setPrice(int price) {
        this.price = price;
    }

    int getAmount() {
        return amount;
    }

    void setAmount(int amount) {
        this.amount = amount;
    }

    @Override
    public String toString() {
        return name + ". $" + price +
               ", amount=" + amount;
    }
}
}

Comments to code - it's proper way to parse all the inputted string and parse it to an object that stores all the data - name, price and amount. Store all parsed objects into array or a list and then calculate max and popular fruit while looping your parsed fruit array

Answer 3

I found some mistake. The most important was in the while condition. Check this out.

public static void main(String[] args) { 
    // TODO code application logic here 
    Scanner input = new Scanner (System.in); 
    String fruitname = null;
    String maxfruit = null;
    int fruitSum = 0;
    int totalSum = 0; 
    int max = 0; 

    System.out.print("Fruit name, " + "price in killogram, number of killogram sold: "); 


    while(!(fruitname = input.next()).equals("stop")){
        fruitSum = input.nextInt() * input.nextInt();
        totalSum += fruitSum;
        if(fruitSum > max){
            maxfruit = fruitname;
            max = fruitSum;
        }

    }

    System.out.println("the earned money of all fruits is " + totalSum); 
    System.out.println("fruit that achieved the largest profit is "+ maxfruit); 
} 
} 

Answer 4

Oh it is reading it.

the problem is that it doesn't do what you want it to do.

the problems with the code I can see are this:

• you are not storing the fruits quantities or prices anywhere, you need to store the values in an array or something (maxFruit,MaxValue) to compare them later.
• when you are reading the fruit values and a "stop" string is input the next step in your code is to wait for the price so it won't get out of the loop even if you input "stop", you need to restructure your scanner loop.

And if it is a beginner class it may be ok, but the code you are writing is not object oriented don't write the logic in the main.

You may want to learn to debug it is a very useful tool when you are learning to code, if you run this program in debug mode , you could see that the values are getting input and everything that is happening, Netbeans and Eclipse have very good debuggers and it would be worth to expend half an hour learning the basics of debugging It certainly helped me a lot when I was starting.

Answer 5

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;

public class FruitSells {
    public static void main(String... args) {
        BufferedReader bufer = new BufferedReader(new InputStreamReader(System.in));
        try {
            String str;
            String[] inarr;
            int sumMoney = 0;
            do {
                str = (String) bufer.readLine();
                inarr = str.split(" ");
                for(int i = 1; i < inarr.length; i += 3) {
                    sumMoney += Integer.parseInt(inarr[i]) * Integer.parseInt(inarr[i + 1]);
                }
                System.out.println(sumMoney);
                sumMoney = 0;
            } while (!str.equals("stop"));


        } catch(IOException ex) {
            System.out.println("Problems with bufer.readLine()");
        }
    }
}

something like this you can modernize it.sorry for eng i can not speak))and write correctly of course))