Copying text to the clipboard using Java

This works for me and is quite simple:

Import these:

import java.awt.datatransfer.StringSelection;
import java.awt.Toolkit;
import java.awt.datatransfer.Clipboard;

And then put this snippet of code wherever you'd like to alter the clipboard:

String myString = "This text will be copied into clipboard";
StringSelection stringSelection = new StringSelection(myString);
Clipboard clipboard = Toolkit.getDefaultToolkit().getSystemClipboard();
clipboard.setContents(stringSelection, null);

For JavaFx based applications.

        //returns System Clipboard
        final Clipboard clipboard = Clipboard.getSystemClipboard();
        // ClipboardContent provides flexibility to store data in different formats
        final ClipboardContent content = new ClipboardContent();
        content.putString("Some text");
        content.putHtml("<b>Some</b> text");
        //this will be replaced by previous putString
        content.putString("Some different text");
        //set the content to clipboard
        clipboard.setContent(content);
       // validate before retrieving it
        if(clipboard.hasContent(DataFormat.HTML)){
            System.out.println(clipboard.getHtml());
        }
        if(clipboard.hasString()){
            System.out.println(clipboard.getString());
        }

ClipboardContent can save multiple data in several data formats like(html,url,plain text,image).

For more information see official documentation

The following class allows you to copy/paste a String to/from the clipboard.

import java.awt.*;
import java.awt.datatransfer.Clipboard;
import java.awt.datatransfer.DataFlavor;
import java.awt.datatransfer.StringSelection;

import static java.awt.event.KeyEvent.*;
import static org.apache.commons.lang3.SystemUtils.IS_OS_MAC;

public class SystemClipboard
{
    public static void copy(String text)
    {
        Clipboard clipboard = getSystemClipboard();
        clipboard.setContents(new StringSelection(text), null);
    }

    public static void paste() throws AWTException
    {
        Robot robot = new Robot();

        int controlKey = IS_OS_MAC ? VK_META : VK_CONTROL;
        robot.keyPress(controlKey);
        robot.keyPress(VK_V);
        robot.keyRelease(controlKey);
        robot.keyRelease(VK_V);
    }

    public static String get() throws Exception
    {
        Clipboard systemClipboard = getSystemClipboard();
        DataFlavor dataFlavor = DataFlavor.stringFlavor;

        if (systemClipboard.isDataFlavorAvailable(dataFlavor))
        {
            Object text = systemClipboard.getData(dataFlavor);
            return (String) text;
        }

        return null;
    }

    private static Clipboard getSystemClipboard()
    {
        Toolkit defaultToolkit = Toolkit.getDefaultToolkit();
        return defaultToolkit.getSystemClipboard();
    }
}

This is the accepted answer written in a decorative way:

Toolkit.getDefaultToolkit()
        .getSystemClipboard()
        .setContents(
                new StringSelection(txtMySQLScript.getText()),
                null
        );