To right justified a JTextField contents we can call the setHorizontalAlignment(JTextField.RIGHT) method of the JTextField class.

package org.kodejava.swing;

import javax.swing.JFrame;
import javax.swing.JTextField;
import javax.swing.SwingUtilities;
import javax.swing.WindowConstants;
import java.awt.Container;
import java.awt.Dimension;
import java.awt.FlowLayout;

public class TextFieldRightJustify extends JFrame {
    public TextFieldRightJustify() {
        initComponents();
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(() -> new TextFieldRightJustify().setVisible(true));
    }

    private void initComponents() {
        setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
        setSize(500, 500);

        Container container = getContentPane();
        container.setLayout(new FlowLayout(FlowLayout.LEFT));

        JTextField textField = new JTextField(15);
        textField.setPreferredSize(new Dimension(100, 20));

        // Right justify the JTextField contents
        textField.setHorizontalAlignment(JTextField.RIGHT);

        container.add(textField);
    }
}