Question

我想要hashmap到数组

我创建了hashmap

<!DOCTYPE html>
<html>
<head>
<title>Cookie Order Form </title>
<link rel="stylesheet" href="Form_Design.css">
</head>
<body>
    <h1>Cookie Order Form</h1>
<p>This form is a cookie order form for customers that purchased cookies from
Daron's Cookies Company and the following below must be filled out in order for each
customer to receive a final message that tells them when their order will be ready.</p>

<!--The customer will be sent to the HTML page named "submit form.html" after they
  click the "Submit this Form" button. The code below does this. -->
<IMG class="Wrap1" SRC="cookie.gif" alt="cookie">
<IMG class="Wrap2" SRC="cookie.gif" alt="cookie2">

<div>
 <form id="cookie_form" name="cookie_form" action="form.html" method="get">

<fieldset>
         <!-- Below sets the title of the form-->
    <legend>Customer Order Form Information:</legend> 


 <!-- Creates the first left label to specify what should be placed in the text box
    the the right of the label. The rest below does the same.-->

  <label for="firstName">First Name:</label>
  <input type="text" id="firstName" name="firstName">
  <span id="firstname_error">*</span><br>

  <label for="orderNumber">Order Number:</label>
  <input type="text" id="orderNumber" name="orderNumber">
  <span id="orderNumber_error">*</span><br>

  <label for="date_of_order">Date of Order:</label>
  <input type="text"  id="date_of_order" name="date_of_order">
  <span id="date_of_order_error">*</span><br>

  <label for="email_address">Email Address:</label>
  <input type="text" id="email_address" name="email_address">
  <span id="email_address_error">*</span><br>

  <label>&nbsp;</label>

  <input type="button" id="form_submission" value="Submit this Form">
  </fieldset>

  </form>

</div>
<div class="clearfix">
</div>
<IMG class="Wrap1" SRC="cookie.gif" alt="cookie">
<IMG class="Wrap2" SRC="cookie.gif" alt="cookie2">
</body>
</html>

并将其放入一些地图数据

然后我将这个hashmap的值转换为数组

    /* Tells HTML5 to find the font-type-face that my OS has and then use that for heading 1
  and also centers the first heading */  

h1{
            font-family:Arial, Helvetica, sans-serif; 
      text-align:center;        
}


/* Tells HTML5 to use any of the font-types for my first paragraph in HTML source file
   if one is not available. Also clears some white space 
   from the left margin of the paragraph and finally tells it to give that paragraph
   a size of 20 pixels. */

p{
            font-family:Arial, Helvetica, sans-serif; 
            padding: 20px;
            font-size:20px;  
}

/* Tells the language to find the only div tag and position it 0 pixels from 
  the top, 1.56 pixels to the right, and 1.88 pixels from the bottom. */


label{
  float: left; 
  width: 11em; 
  text-align: right;
        font-family:Arial, Helvetica, sans-serif; 

}
  input{
      margin-left: 1em; 
      margin-bottom:.5em; 
  }
  span{
      color: red; 
  }

legend{ 
         font-family:Arial, Helvetica, sans-serif; 


} 

/* All of the TextWrap classes are just for positioning and floating the four 
same images around the form input information        */

.Wrap1{
             float:right;
             margin:40px;
             width:200px; 
             height:200px;
}
.Wrap2{
             float:left;
             margin:40px;
             width:200px; 
             height:200px;
}

.clearfix {
  clear: both;
}

但是错误发生了;

Map<Integer,File> selectedFiles = new Hashmap<>();

我知道当我想要将hashmap的值设置为数组时，请使用.values.toArray（），但也许它不是正确的;

这种方式错了吗？

Answer 1

Map<Integer, File> selectedFiles = new HashMap<>();
    selectedFiles.put(1, null);

    File[] files = selectedFiles.values().toArray(
            new File[selectedFiles.size()]);

    System.out.println(files);// We will get the object [Ljava.io.File;@15db9742

阵列。不带参数的toArray会创建一个对象数组，因为列表的类型信息会在运行时丢失。

Answer 2

请使用以下代码将HashMap转换为数组，您可以在您的情况下将字符串更改为文件。

   //Creating a HashMap object

    HashMap<String, String> map = new HashMap<String, String>();

    //Getting Collection of values from HashMap

    Collection<String> values = map.values();

    //Creating an ArrayList of values

    ArrayList<String> listOfValues = new ArrayList<String>(values);

   // Convert ArrayList to Array

   String stringArray[]=listOfValues.toArray(new String[listOfValues.size()])

我如何将hashmap转换为数组？

2 个答案: