arraylist y/n 在java中输入值

Question

我需要创建一个包含 3 个字段（每个字段）的数组列表，此代码不起作用，需要帮助修复它。这项任务似乎很简单，但我无法弄清楚出了什么问题。我正在运行 netbeans

这是我目前所拥有的

import java.util.Scanner;
import java.util.ArrayList;
public class scientist1
{
    public static void main (String[] args)
    {
    Scanner kbd1 = new Scanner(System.in);
    ArrayList<Document> someStuff = new ArrayList<Document>();
    char quit = 'Y';
    String scientist, field, greatIdea;

        while (quit == 'Y')
        {
            System.out.print("\n Scientists name: ");
            scientist = scan.next();
            System.out.print(" scientists field: ");
            field = scan.next();
            System.out.print(" Scientists great Ideas: ");
            greatIdea = scan.nextInt();
            someStuff.add (new Document(field, scientist, greatIdea));
            System.out.print(" Enter Another Scientist? (Y/N)");
            String word = scan.next();
            word = word.toUpperCase();
            quit= word.charAt(0);
        }
        for(Document stuff : someStuff)
        System.out.println(stuff);
}
}



public class Document
{
public static String scientist, field;
private int greatIdea;
public Document (String Last, String First,String Idea)
{
    scientist = First;
    field = Last;
    greatIdea = Idea;
}
public String toString ()
{
    return "\n\n Name: " + field + ", " + scientist + "\n Document Code: " + greatIdea + "\n";
}
public boolean equals (Object other)
{
    return (field.equals(((Document)other).getLast())&&
    scientist.equals(((Document)other).getFirst()));
}
public int compareTo (Object other)
{
    int result;
    String otherFirst = ((Document)other).getFirst();
    String otherLast = ((Document)other).getLast();
    if (field.equals(otherLast))
        result = scientist.compareTo(otherFirst);
    else
        result = field.compareTo(otherLast);
    return result;
}
public String getFirst ()
{
    return scientist;
}
public String getLast ()
{
    return field;
}
}

Answer 1

如果您使用的是 Java 8，则可以使用 List.sort 执行此操作，如下所示：

someStuff.sort(Comparator.comparing(Document::getScientist));

如果您使用低于 Java 8 的版本，则需要通过实现 Comparator 接口来执行此操作，然后使用 Collections.sort 对对象进行排序。

Answer 2

好的，向您展示如何做到这一点，并让您有机会解决代码中的问题，我举了一个例子。像 nerdlyist 一样，为了简单起见，我将 a 类嵌套在主类中。我还使用了比较器类中 hagmic 建议的内置排序功能。这意味着它可以节省时间和精力，因为您不必编写自己的比较器。

import java.util.Scanner;
import java.util.List;
import java.util.ArrayList;
import java.util.Comparator;

public class Test {
    private Scanner scan = new Scanner(System.in);
    private List<LayoutOfScientist> scientistsNames = new ArrayList<LayoutOfScientist>();
    private String name, field, idea;
    private boolean continueLoop = true;
    private int countTo3 = 0;

    private void run() {
        while(countTo3<3&&continueLoop) {
            if(countTo3>0) {
                System.out.println("Would you like to add another scientist? (Y/N)");
            }

            if(countTo3 == 0 || scan.nextLine().equalsIgnoreCase("y")) {
                System.out.println("Please enter the scientist's name:");
                name = scan.nextLine();
                System.out.println("Please enter the scientist's field:");
                field = scan.nextLine();
                System.out.println("Please enter the scientist's idea:");
                idea = scan.nextLine();
                scientistsNames.add(new LayoutOfScientist(name, field, idea));
            } else {
                continueLoop = false;
            }
            countTo3++;
        }

        scientistsNames.sort(Comparator.comparing(LayoutOfScientist::getScientistName));
        for(LayoutOfScientist lOS : scientistsNames) {
            System.out.println(lOS.getScientistName() + ", " + lOS.getScientistField() + ", " + lOS.getScientistIdea());
        }
    }

    private class LayoutOfScientist {
        private String scientistName, scientistField, scientistIdea;

        private LayoutOfScientist(String scientistName, String scientistField, String scientistIdea) {
            this.scientistName = scientistName;
            this.scientistField = scientistField;
            this.scientistIdea = scientistIdea;
        }

        public String getScientistName() {
            return scientistName;
        }

        public String getScientistField() {
            return scientistField;
        }

        public String getScientistIdea() {
            return scientistIdea;
        }
    }

    public static void main(String[] args) {
        new Test().run();
    }
}

示例输入

Dan
Space
2
Y
Tom
Earth
3
Y
Bob
Space
6

输出

Bob, Space, 6
Dan, Space, 2
Tom, Earth, 3

Answer 3

处理这个问题的一种方法是声明一个字符串数组的arraylist。 所以像：

ArrayList<String[]> someStuff = new ArrayList<String[]>;

此方法的一个问题是，每次将新元素附加到 someStuff 时，都需要初始化该单独的 String 数组： 例如：

someStuff.add(new String[] {"Scientist", "Field", "Idea"});

或者：

someStuff.add(new String[3]);

此时我建议使用 2 个字符串函数中的任何一个：

compareTo(String str)

或者：

compareToIgnoreCase(String str)

在按科学家姓名组织 ArrayList 的排序函数中。

Answer 4

只有 3 个小错误..

1. Scanner 的实例名为 kbd1，但用作 scan

   Scanner kbd1 = new Scanner(System.in);

//使用like科学家=scan.next();

//用作

Scanner kbd1 = new Scanner(System.in);
scientist = kbd1.next();

1. String greatIdea;//字符串变量 //输入为int

   greatIdea = kbd1.nextInt();//错误

2. 在 Document 类中

private int greatIdea;//必须是String

就是这样，你可以走了。

PS: 格式不当见谅

Answer 5

似乎问题是让您的文档进入列表而不是排序。为此，您应该解决被吐出的 8 个错误。下面的代码用一些注释进行了清理。主要的变化是为了便于编译，我将 Document 做成了一个嵌套类（您可以将其取出并导入）。

import java.util.Scanner;
import java.util.ArrayList;
public class scientist1 {
    static class Document  {
        private String scientist, field, greatIdea; //Stay consistent with private and removed static.

        public Document  (String last, String first, String idea)
        {
            scientist = first;
            field = last;
            greatIdea = idea;
        }
        public String toString ()
        {
            return "\n\n Name: " + field + ", " + scientist + "\n Document  Code: " + greatIdea + "\n";
        }
        public boolean equals (Object other)
        {
            return (field.equals(((Document )other).getLast())&&
            scientist.equals(((Document )other).getFirst()));
        }
        public int compareTo (Object other)
        {
            int result;
            String otherFirst = ((Document )other).getFirst();
            String otherLast = ((Document )other).getLast();
            if (field.equals(otherLast))
                result = scientist.compareTo(otherFirst);
            else
                result = field.compareTo(otherLast);
            return result;
        }
        public String getFirst ()
        {
            return scientist;
        }
        public String getLast ()
        {
            return field;
        }
    }
    public static void main (String[] args) {
        Scanner scan = new Scanner(System.in);
        ArrayList<Document > someStuff = new ArrayList<Document >();
        char quit = 'Y';
        String scientist, field, greatIdea;

        while (quit == 'Y')
        {
            System.out.print("\n Scientists name: ");
            scientist = scan.next();
            System.out.print(" scientists field: ");
            field = scan.next();
            System.out.print(" Scientists great Ideas: ");
            greatIdea = scan.next();
            someStuff.add(new Document (field, scientist, greatIdea));
            System.out.print(" Enter Another Scientist? (Y/N)");
            String word = scan.next();
            word = word.toUpperCase();
            quit= word.charAt(0);
        }
        for(Document  stuff : someStuff){
            System.out.println(stuff);
        }
    }
}