Question

我是Java的新手。我当前的程序循环遍历一个块，该块要求用户在控制台中输入，直到他们键入的值等于完成。我想将用户键入的每个值存储在一个类属性的数组中。当我尝试附加此数组时，出现错误Error:(59, 18) java: not a statement。我的代码如下。我将指出代码内部发生错误的行。谢谢你的时间！

package com.example.java;

import java.util.Scanner;

public class Main {

    public static void main(String[] args) {

        Scanner scanner = new Scanner(System.in);

        System.out.println("Welcome to the musical key calculator!");
        System.out.println("Enter your notes one at a time.");
        System.out.println("Use uppercase letters A-G and # for sharp and b for flat.(Ex. Eb)");
        System.out.println("Remember that E# and B# do not exist in music!");
        System.out.println("When you have entered all of your notes, type 'done'");
        System.out.println("------------------------------------------------------------------");

        boolean finished = false;

        Scale YourScale = new Scale();
        while(finished == false) {

            System.out.print("Enter a note: ");

            String note = scanner.nextLine();

            if (note == "done'") {

                finished = true;

            } else {

                YourScale.addNote(note);

            }

        }

        if(finished == true){

            StringBuilder output = new StringBuilder("Your notes are ");
            String[] completedNotes = YourScale.notes;
            for (int i = 0; i < completedNotes.length; i++) {

                output.append(completedNotes[i] + " ");

            }

        }

    }

    public static class Scale {

        public String[] notes = {};

        public void addNote(String note){

            notes[] = note; //Error occurs here.

        }
    }
}

Answer 1

Java数组是固定长度的，而不是您创建（或填充数组）的方式。我更喜欢使用Collection之类的，

public List<String> notes = new ArrayList<>();
public void addNote(String note){
    notes.add(note);
}

但是，你可以使用Arrays.copyOf(T[], int)和

之类的东西

public String[] notes = new String[0];
public void addNote(String note){
    int len = notes.length;
    notes = Arrays.copyOf(notes, len + 1);
    notes[len] = note;
}

最后，您不会使用String

测试==平等

if (note == "done'") {

应该是

if (note.equals("done")) {

Answer 2

notes是一个String数组，这意味着它里面有很多String个对象。你也将它初始化为一个空数组。数组应该有固定的大小。

//Declare a variable notes, and initialize it as an empty array?
public String[] notes = {};

public void addNote(String note)
{
    //This doesn't make sense in java - it's syntax is wrong
    notes[] = note;
}

如果你想使用数组，这就是一个例子：

//Declare a variable notes, and initialize it as an array of 
//specific size (I used 5 as example)
public String[] notes = new String[5];

public void addNote(String note)
{
    //Here you should have some short of counter that counts in which
    // position of the array you will save 'note' or just run a 'for'
    //loop and the first element that is not initialized can get the note

    for (int i = 0; i < notes.length; i++)
        if (notes[i] == null)
        {
            notes[i] = note;
            break;
        }
}

虽然此方法允许您保存固定大小，这在您的情况下是不可取的，但它使用Array并且可以帮助您了解如何使用它们。

如果要正确实施，请使用ArrayList。 ArrayList是一个数组，您可以在其中添加新元素并将其删除。您可以在线找到大量有关如何使用它们的文档。

Answer 3

您正在尝试将String分配给String数组。您可能打算将其添加到数组中。

为什么这不是一个陈述＆＃34;在java？

3 个答案: