How to Use Tables in Java
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In Java, tables are used to arrange data into columns and rows. A column is space that runs horizontally on a table, while a row is a space that runs horizontally in your table. The intersection between a column and a row is called a cell and is used to hold singular piece of data.
In Java, developers can use the JTable method to create a table in their applications. JTable is a Swing component that inherits from the JComponent class.
How to Create a Table in Java
To create a table, you need to make an instance of the JTable class. You need to provide two arguments (row and column) in its constructor for the table to be constructed, as shown in this example code snippet:
JTable table = new JTable (row, column);
The row and column values can consist of two integer values, like below:
JTable table = new JTable (5,3);
The above statement creates a table with 5 rows and 3 columns.
Instead of providing the JTable constructor with integers, programmers can also supply a two dimensional array for the data in each row, and a one dimensional array for the column names. Here is how you can use arrays to create a table in Java:
JTable(Object[][] rowData, Object[] columnNames)
Here is some example code showing how to create a table in Java and fill it with data:
import javax.swing.*; import javax.swing.table.*; import java.awt.*; class Table< public static void main(String args[])< JFrame frame = new JFrame(); String[] columnNames = ; Object[][] data = < , , , , >; JTable table = new JTable(data, columnNames); frame.add(table); frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); frame.setSize(400,400); frame.setLocationRelativeTo(null); frame.setVisible(true); > >
If you run this code in your integrated development environment (IDE) or code editor, it will produce the following output:
When you click on any one of the above cells, you will notice that the data in it is editable. This is not a particularly desirable feature if you are just presenting data to your user. Also, all the data is treated as a string when in its presentation to a user.
Another point of concern is that, in case you were querying a database object for particular values, you would have to copy all values to an array or vector.
To avoid these problems, you can instead create your Java table using a model.
How to Create a Table Using a Model in Java
First, it is important to understand how table data is handled. All tables (including a table created using JTable()) use a table model to manage their data. When developers do not provide a table model to the constructor of JTable, an instance of DefaultTableModel will be automatically created for it. Therefore, if you need to use a custom model, you need to provide it to the JTable constructor, as shown in this example code:
JTable table = new JTable(new MyTableModel());
To define a table model, programmers need to create a class that extends the AbstractTableModel class:
class MyTableModel extends AbstractTableModel
In your table model, you can include the data for your rows and column names, just as shown in the earlier JTable example. To ensure that your table model class is a concrete class, you need to implement the following three methods of AbstractTableModel:
public int getRowCount(); public int getColumnCount(); public Object getValueAt(int row, int column);
You can implement more methods, but you must ensure that the above methods are among those you implement. You can find the description of other methods from the official Oracle API docs.
The code example below shows how you can use a table model in Java:
import javax.swing.*; import javax.swing.table.*; import java.awt.*; class TableUsingModel < public static void main(String args[])< JFrame frame = new JFrame(); JTable table = new JTable(new MyTableModel()); frame.add(table); frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); frame.setSize(400,400); frame.setLocationRelativeTo(null); frame.setVisible(true); >> class MyTableModel extends AbstractTableModel < String[] columnNames = ; Object[][] data = < , , , , >; public int getRowCount() < return data.length; >public int getColumnCount() < return columnNames.length; >public Object getValueAt(int row, int col) < return data[row][col]; >>
This results in the following output (Display):
This time, if you try double-clicking on any cell, you will notice that it is not editable.
How to Manage Column Width & Height in Java
If you want to set the height of rows, you can use the setRowHeight() method.
JTable table = new JTable(data, columnNames); table.setRowHeight(80);
The above example sets the height of each row 80 pixels.
To set the width of columns, you can use the setPreferredWidth() method. First, you need to create a column model of type TableColumnModel. Then you can get the particular column you want and then set its preferred width. Here is some example code showing how to set the column width of a table in Java:
TableColumnModel columnModel = table.getColumnModel(); columnModel.getColumn(2).setPreferredWidth(200);
Final Thoughts on Java Tables
In this programming tutorial, programmers learned how to use JTable, or a table model, to create a table in Java. The code examples shown above add the tables directly to the JFrame container. However, you can instead add your table to a scroll pane so that your user can easily navigate through the data when it does not fit its container.
Create Table in Java
- Use JTable to Create Table in Java
- Use Guava Library to Create Table in Java
In this article, we will look at tables in Java.
We will talk about two ways to use tables in the following sections. A basic table has rows and columns to show data in a readable structure.
Use JTable to Create Table in Java
In this example, we use the JTable component of the GUI library Swing in Java. We create a JFrame object to show the table in the window; then, we create a two-dimensional array tableData containing the raw data.
We create an array with the field names to show the column fields. Now we create an object of JTable and pass the tableData and tableColumn as arguments in the constructor.
We set the size of the JTable using the setBounds() method. To make the table scrollable when the table data grows more than the size, we use JScrollPane , which shows scroll bars when the components go beyond the view.
At last, we add the JScrollPane object to the JFrame and set the size and visibility of the frame.
import javax.swing.*; public class JavaExample public static void main(String[] args) JFrame jFrame = new JFrame(); String[][] tableData = <"01", "Adam", "1986">, "02", "John", "1990">, "03", "Sam", "1989">, "04", "Derek", "1991">, "05", "Ben", "1981">>; String[] tableColumn = "ID", "FIRST NAME", "BIRTH YEAR">; JTable jTable = new JTable(tableData, tableColumn); jTable.setBounds(30, 40, 230, 280); JScrollPane jScrollPane = new JScrollPane(jTable); jFrame.add(jScrollPane); jFrame.setSize(350, 300); jFrame.setVisible(true); > > 
Use Guava Library to Create Table in Java
We can also use the Table interface of the com.google.common.collect package, a part of the Guava library. In the program, we create an instance of the HashBasedTable class that implements the Table interface by calling the create() and returns an object of the Table type.
The Table has three type parameters: first is the type of keys of the row, second is the type of column keys, and the last parameter is the type of values mapped to the keys. The keys of rows and columns are associated with a single value.
We call the put() method using the Table object. In the put() function, we pass three arguments: the key for the row, the column, and the last are for the value to be mapped.
We can perform several operations using the Table interface and its classes. The row() and column() are two methods to fetch the values and the keys corresponding to the row or column key.
When we call table.row() and pass the row key, we get a map in return. We use this getRows map to call the entrySet() that returns a Set of the elements.
Now we use the Set to get the stringEntry of Map.Entry that gives a map entry. We fetch the key and the value using the method getKey and getValue .
We follow the same steps to get the row key and the value using the column() method. Methods like rowMap() and columnMap() return the whole table data.
The rowKeySet() returns all the row keys in the table.
import com.google.common.collect.HashBasedTable; import com.google.common.collect.Table; import java.util.Map; public class JavaExample public static void main(String[] args) TableString, String, String> table = HashBasedTable.create(); table.put("Adam", "1990", "101"); table.put("John", "1994", "102"); table.put("Jane", "1991", "103"); table.put("John", "1995", "104"); table.put("Adam", "1996", "105"); table.put("Sam", "1991", "106"); table.put("Watson", "1994", "107"); table.put("Kelly", "1994", "108"); table.put("Martha", "1995", "109"); table.put("Billy", "1994", "107"); MapString, String> getRows = table.row("Adam"); System.out.println("Row Results: "); for (Map.EntryString, String> stringEntry : getRows.entrySet()) System.out.println("Birth Year: " + stringEntry.getKey() + " | ID: " + stringEntry.getValue()); > System.out.println(); MapString, String> getCols = table.column("1994"); System.out.println("Column Results: "); for (Map.EntryString, String> stringEntry : getCols.entrySet()) System.out.println("First Name: " + stringEntry.getKey() + " | ID: " + stringEntry.getValue()); > System.out.println(); System.out.println("Row Map Data Of Table: " + table.rowMap()); System.out.println(); System.out.println("All The Keys: " + table.rowKeySet()); > > Row Results: Birth Year: 1990 | ID: 101 Birth Year: 1996 | ID: 105 Column Results: First Name: Billy | ID: 107 First Name: John | ID: 102 First Name: Watson | ID: 107 First Name: Kelly | ID: 108 Row Map Data Of Table: , Billy=, John=, Watson=, Jane=, Sam=, Martha=, Kelly=> All The Keys: [Adam, Billy, John, Watson, Jane, Sam, Martha, Kelly] Rupam Saini is an android developer, who also works sometimes as a web developer., He likes to read books and write about various things.