Question

在我的代码中创建搜索方法以搜索字符串时，我一直收到此错误。我已经经历了很多试图解决这个问题的例子，但我找不到。感谢您的帮助，并建议您给予。

public class runNote {

public static void main(String[] args) {
    // TODO Auto-generated method stub
    Notebook note = new Notebook();
    note.storeNote("happy");
    note.storeNote("hello there");
    note.storeNote("work at 5");
    note.storeNote("BBQ Time");
    note.storeNote("UNI!!!!");
    note.storeNote("Dont miss lecture at 9:15");
    System.out.println(note.numberOfNotes());
    note.showNote(1);
    note.searchNotes("hap");

}}




public class Notebook{


/**
 * Perform any initialization that is required for the
 * notebook.
 */
public Notebook()
{
    notes = new ArrayList();
}

/**
 * Store a new note into the notebook.
 * @param note The note to be stored.
 */
public void storeNote(String note)
{
    notes.add(note);
}

/**
 * @return The number of notes currently in the notebook.
 */
public int numberOfNotes()
{
    return notes.size();
}

/**
 * A simple search engine to find the correct notes.
 */
public void searchNotes(String search){ 
    for (String item : notes){
        if (item.contains(search)){
        System.out.println(item);
        }
    }
}

/**
 * Show a note.
 * @param noteNumber The number of the note to be shown.
 */
public void showNote(int noteNumber)
{
    if(noteNumber < 0) {
        // This is not a valid note number, so do nothing.
    }
    else if(noteNumber < numberOfNotes()) {
        // This is a valid note number, so we can print it.
        System.out.println(notes.get(noteNumber));
    }
    else {
        // This is not a valid note number, so do nothing.
    }
}
}

Answer 1

你在这一行有例外：

 for (String item : notes)

notes是一个ArrayList声明为原始类型，虽然我没有看到声明我可以看到这行初始化：

notes = new ArrayList();

从Object类型看到它的元素您需要使用notes类型声明ArrayList<String>，例如：

  ArrayList<String> notes = new ArrayList<>();

Answer 2

将笔记作为全局变量添加到您的班级

public class Notebook{
ArrayList<String> notes = null;

....
}

在构造函数中，执行：

public Notebook()
{
    notes = new ArrayList<String>();
}

Answer 3

试试这个：notes = new ArrayList<String>();

Answer 4

您没有声明注释变量

public class Notebook{
  private ArrayList<String> notes;
...

类型不匹配无法从元素类型对象转换为字符串

4 个答案: