ArrayList for循环仅适用于第一个元素

Question

I'm working on a project in Javascript that requires me to write a class with a method that prints the information for a Tree object in a certain format. This is my toString method so far (the t.toString() inside the method is a reference to a different toString method in a different class). It's supposed to display the information for one Tree object, then go to a new line and display the information for the next Tree object.

public String toString() 
    {
        for (Tree t : db) 
        {
            return t.toString() + "\n";
        }

        return null;
    }

I tested the method using this code.

 TreeDB trees = new TreeDB();

        Tree oak = new Tree("Oak", 24, 27);
        Tree maple = new Tree("Maple", 8, 38);
        Tree spruce = new Tree("Spruce", 11, 32);

        trees.add(oak);
        trees.add(maple);
        trees.add(spruce);

        System.out.println(trees.toString());

It prints the information for Oak, but not for Maple or Spruce. I'm assuming something is wrong with the header for my for-loop. Can someone help me figure out how to make it print the information for all of the Tree objects?

Answer 1

(a) Please recheck your loop.

(b) Your question says you're working on a Javascript project yet the code you posted is in Java.

Answer 2

You exit the function after reading the first element, returning its String representation. Use a StringBuffer to store all elements :

    public String toString() 
    {
        StringBuffer result = new StringBuffer();
        for (Tree t : db) 
        {
            result.append(t.toString()).append("\n");
        }

        return result.toString();
    }

Answer 3

In your for each loop you're returning the first value.

Use StringBuilder (sb) to store (append) all the values and then return sb.toString()