如何使用数据列表检查多行输入

Question

I am trying to get java to take an input of x amount of lines and get it to check an if else tree for the output of each one. I can only get it to check one line of input though. Please help, I am new to programming Java. This is what I have so fat:

package Javatest;
import java.util.Scanner;

public class Jtest {

  public static void main(String[] args) {

    Scanner input = new Scanner(System.in);
    System.out.println("Enter Part Number: ");
    String price = input.nextLine();

    if("700212129".equals(price)){
        System.out.println("$280.00");
    }else{
      if("100010B".equals(price)){
        System.out.println("$52.50");
      }else{
        if("100030B".equals(price)){
          System.out.println("$7.18");
        }else{
          if("1189A-BELDEN".equals(price)){
            System.out.println("$140.00");
          }else{
            System.out.println("#N/A");
            return;     
          }             
        }
      }
    }
  }
}

Answer 1

Try to extract logic of each part. This is an implementation which separately initializes the list, waits for input, scrolls down stuffs and searches for code to extract the price.

package Javatest;

import java.util.LinkedHashSet;
import java.util.Scanner;
import java.util.Set;

public class Jtest {

    private static final String EXIT_CODE = "exit"; 
    private Set<Stuff> stuffs = new LinkedHashSet<Stuff>();

    public static void main(String[] args) {
        Jtest jtest = new Jtest();
        jtest.initList();
        while(true) {
            System.out.println("Enter Part Number: ");
            Scanner input = new Scanner(System.in);
            String inputLine = input.nextLine();
            if(inputLine.equals(EXIT_CODE)){
                System.out.println("Exiting");
                break;
            }
            String price = jtest.findPrice(inputLine);
            System.out.println("Price: " + price);
        }
    }

    private void initList() {
        stuffs.add(new Stuff("700212129", "$280.00"));
        stuffs.add(new Stuff("100010B", "$52.50"));
        stuffs.add(new Stuff("100030B", "$7.18"));
        stuffs.add(new Stuff("1189A-BELDEN", "$140.00"));
    }

    private String findPrice(String code) {
        for(Stuff stuff: stuffs){
            if(code.equals(stuff.getCode())){
                return stuff.getPrice();
            }
        }
        return "#N/A";      
    }

    public static class Stuff {

        private String code;
        private String price;

        public Stuff(String code, String price) {
            this.code = code;
            this.price = price;
        }

        public String getPrice(){
            return this.price;          
        }

        public String getCode(){
            return this.code;           
        }
    }
}

This is a very basic implementation but it can inspire you to build a better solution.

Answer 2

the first thing you want to do is learn about splitting/decoupling methods from your main. Its bad practise to just write all of your code in one place.

What i would do is write this in two parts:

First create a procedure to return a string from a single string input and include your nested if statement inside.

private static string GetString(string inputData)
{
         if("700212129".equals(inputData)){
            return "$280.00";
        }else{
            if("100010B".equals(inputData)){
                return "$52.50";
            }else{
                if("100030B".equals(inputData)){
                    return "$7.18";
                }else{
                    if("1189A-BELDEN".equals(inputData)){
                       return "$140.00";
                    }else{
                        return "#N/A";

      }               
}

Then in Main(), use a loop to constantly check any input you have typed, using a While loop would be a good example as you can use an escape clause to stop the loop/program.

public static void main(String[] args) {

    Scanner input = new Scanner(System.in);
    System.out.println("Enter Part Number: ");
    String value = input.nextLine();
    String output;
    While(value != "E")
     {
      output = GetString(value);
      System.out.println("Value is: " + output);
     }
}

I would also suggest changing your nested If statement to a Switch/Select statement.