Java 将 ArrayList 转换为二维数组
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Converting an ArrayList into a 2D Array
提问by Anto
In Java how do you convert a ArrayList into a two dimensional array Object[][]?
在 Java 中，如何将 ArrayList 转换为二维数组 Object[][]？
From comments: I will describe you the problem with more details: an XML file includes a list of contacts (e.g. name, address...). The only way I can obtain this information is through an ArrayList, which will be given to me. As I need to store the content of this array list in a Java Swing table in an ordered manner, I was thinking to convert it into a two dimensional array of objects
来自评论：我将用更多细节向您描述问题：一个 XML 文件包括一个联系人列表（例如姓名、地址...）。我能获得这些信息的唯一方法是通过一个 ArrayList，它将提供给我。由于我需要以有序的方式将此数组列表的内容存储在 Java Swing 表中，因此我想将其转换为对象的二维数组
采纳答案by Anto
I managed to find "a way" to do so, knowing the number of attributes each contacts has (6). So considering an ArrayList listofContacts
我设法找到了这样做的“方法”，知道每个联系人具有的属性数量（6）。所以考虑一个ArrayList listofContacts
int numberOfContacts = listofContacts.size()/6;
Object[][] newArrayContent = new Object[numberOfContacts][6];
for(int x = 0; x<numberOfContacts; x++){
for(int z = 0; z < 6; z++){
int y = 6 * x;
newArrayContent [x][z] = list.get(y+z);
System.out.println(newArrayContent [x][z].toString());
}
}
回答by Carlos Tasada
What you really want is to sort the ArrayList. To do that your Contacts class must implement a Comparator method.
您真正想要的是对 ArrayList 进行排序。为此，您的 Contacts 类必须实现 Comparator 方法。
Check the next page for an example: http://www.java-examples.com/sort-java-arraylist-descending-order-using-comparator-example
检查下一页以获取示例：http: //www.java-examples.com/sort-java-arraylist-descending-order-using-comparator-example
回答by Ravi Gupta
回答by Stephen C
The simple way is to add a method to the Contactlike this:
简单的方法是添加一个方法，Contact如下所示：
public Object[] toObjectArray() {
return new Object[] { getName(), getAddress, /* ... */ };
}
and use it like this:
并像这样使用它：
ArrayList<Contact> contacts = /* ... */
Object[][] table = new Object[contacts.size()][];
for (int i = 0; i < contacts.size(); i++) {
table[i] = contacts.get(i).toObjectArray();
}
回答by Adam Paynter
I presume you are using the JTable(Object[][], Object[])constructor.
我假设您正在使用JTable(Object[][], Object[])构造函数。
Instead of converting an ArrayList<Contact>into an Object[][], try using the JTable(TableModel)constructor. You can write a custom class that implements the TableModelinterface. Sun has already provided the AbstractTableModelclass for you to extend to make your life a little easier.
不要将 an 转换ArrayList<Contact>为 an Object[][]，而是尝试使用JTable(TableModel)构造函数。您可以编写一个实现该TableModel接口的自定义类。Sun 已经提供了AbstractTableModel课程供您扩展，让您的生活更轻松。
public class ContactTableModel extends AbstractTableModel {
private List<Contact> contacts;
public ContactTableModel(List<Contact> contacts) {
this.contacts = contacts;
}
public int getColumnCount() {
// return however many columns you want
}
public int getRowCount() {
return contacts.size();
}
public String getColumnName(int columnIndex) {
switch (columnIndex) {
case 0: return "Name";
case 1: return "Age";
case 2: return "Telephone";
// ...
}
}
public Object getValueAt(int rowIndex, int columnIndex) {
Contact contact = contacts.get(rowIndex);
switch (columnIndex) {
case 0: return contact.getName();
case 1: return contact.getAge();
case 2: return contact.getTelephone();
// ...
}
}
}
Later on...
稍后的...
List<Contact> contacts = ...;
TableModel tableModel = new ContactTableModel(contacts);
JTable table = new JTable(tableModel);
回答by peng
Try this:
尝试这个：
ArrayList<Integer> list = new ArrayList<Integer>();
list.add(..);
list.add(..);
list.add(..);
list.add(..);
list.add(..);
list.add(..);
int[][] a = new int[list.size()][list.size()];
for(int i =0; i < list.size(); i++){
for(int j =0; j <list.size(); j++){
a[i][j]= list.get(j +( list.size() * i));
}
}
回答by Jerry Lamola
public static String[][] convertListIntoArrayObj(List<TeamMenuSelected> possibilities) {
int numberOfColums = 2;
int numberOfRows = possibilities.size();
String[][] values = new String[numberOfRows][numberOfColums];
for(int x=0; x<possibilities.size(); x++) {
TeamMenuSelected item = possibilities.get(x);
values[x][0] = item.getTeamName();
values[x][1] = item.getTeamCuisine();
}
return values;
}
回答by Iyush
ArrayList<String> arrayList = new ArrayList<String>();
arrayList.add("element_1");
arrayList.add("element_2");
arrayList.add("element_3");
arrayList.add("element_4");
int k=0;
int row = 2, col = 2;
Object[][] objArray = new Object[row][col];
for(int i = 0 ; i < row; i++) {
for(int j = 0; j < col; j++) {
objArray[i][j] = arrayList.get(k);
k++;
if(k > arrayList.size()) {
break;
}
}
}
for(int i = 0 ; i < row; i++) {
for(int j = 0; j < col; j++) {
System.out.println("Row no "+i+" col no "+j+" "+objArray[i][j] );
}
}
}
