Task: GUI enabling_disabling of controls
Go: package main

import (
    "github.com/gotk3/gotk3/gtk"
    "log"
    "math/rand"
    "strconv"
    "time"
)

func validateInput(window *gtk.Window, str string) (int64, bool) {
    i, err := strconv.ParseInt(str, 10, 64)
    if err != nil {
        dialog := gtk.MessageDialogNew(
            window,
            gtk.DIALOG_MODAL,
            gtk.MESSAGE_ERROR,
            gtk.BUTTONS_OK,
            "Invalid value",
        )
        dialog.Run()
        dialog.Destroy()
        return 0, false
    }
    return i, true
}

func check(err error, msg string) {
    if err != nil {
        log.Fatal(msg, err)
    }
}

func processState(i int64, entry *gtk.Entry, ib, db *gtk.Button) {
    if i == 0 {
        entry.SetSensitive(true)
    } else {
        entry.SetSensitive(false)
    }
    if i < 10 {
        ib.SetSensitive(true)
    } else {
        ib.SetSensitive(false)
    }
    if i > 0 {
        db.SetSensitive(true)
    } else {
        db.SetSensitive(false)
    }
}

func main() {
    rand.Seed(time.Now().UnixNano())
    gtk.Init(nil)

    window, err := gtk.WindowNew(gtk.WINDOW_TOPLEVEL)
    check(err, "Unable to create window:")
    window.SetTitle("Rosetta Code")
    window.SetPosition(gtk.WIN_POS_CENTER)
    window.Connect("destroy", func() {
        gtk.MainQuit()
    })

    box, err := gtk.BoxNew(gtk.ORIENTATION_HORIZONTAL, 1)
    check(err, "Unable to create box:")
    box.SetBorderWidth(1)

    label, err := gtk.LabelNew("Value:")
    check(err, "Unable to create label:")

    entry, err := gtk.EntryNew()
    check(err, "Unable to create entry:")
    entry.SetText("0") 
    entry.SetSensitive(true)

    
    ib, err := gtk.ButtonNewWithLabel("Increment")
    check(err, "Unable to create increment button:")
    ib.SetSensitive(true)

    
    db, err := gtk.ButtonNewWithLabel("Decrement")
    check(err, "Unable to create decrement button:")
    db.SetSensitive(false)

    entry.Connect("activate", func() {
        
        str, _ := entry.GetText()
        i, ok := validateInput(window, str)
        if !ok {
            entry.SetText("0")
        }
        processState(i, entry, ib, db)
    })

    ib.Connect("clicked", func() {
        
        str, _ := entry.GetText()
        i, _ := validateInput(window, str)
        i++
        entry.SetText(strconv.FormatInt(i, 10))
        processState(i, entry, ib, db)
    })

    db.Connect("clicked", func() {
        
        str, _ := entry.GetText()
        i, _ := validateInput(window, str)
        i--
        entry.SetText(strconv.FormatInt(i, 10))
        processState(i, entry, ib, db)
    })

    box.PackStart(label, false, false, 2)
    box.PackStart(entry, false, false, 2)
    box.PackStart(ib, false, false, 2)
    box.PackStart(db, false, false, 2)
    window.Add(box)

    window.ShowAll()
    gtk.Main()
}

Java: import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JTextField;
import javax.swing.SwingUtilities;

public class Interact extends JFrame{
	final JTextField numberField;
	final JButton incButton, decButton;
	
	public Interact(){
		
		setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); 
		
		numberField = new JTextField();
		incButton = new JButton("Increment");
		decButton = new JButton("Decrement");
		
		numberField.setText("0");
		decButton.setEnabled(false);
		
		
		numberField.addKeyListener(new KeyListener(){
			@Override
			public void keyTyped(KeyEvent e) {
				
				if(!Character.isDigit(e.getKeyChar())){
					
					e.consume();
				}else if(Character.isDigit(e.getKeyChar())){
					
					
					
					SwingUtilities.invokeLater(new Runnable() {
						@Override
						public void run() {
							String text = numberField.getText();
							if(text.isEmpty()){
								numberField.setText("0");
								decButton.setEnabled(false);
								incButton.setEnabled(true);
								return;
							}
							if(Long.valueOf(text) <= 0){
								decButton.setEnabled(false);
								incButton.setEnabled(true);
							}else if(Long.valueOf(text) >= 10){
								incButton.setEnabled(false);
								decButton.setEnabled(true);
							}else{
								incButton.setEnabled(true);
								decButton.setEnabled(true);
							}
						}
					});
				}
			}
			@Override
			public void keyReleased(KeyEvent e){}
			@Override
			public void keyPressed(KeyEvent e){
				
				
				if(e.getKeyCode() == KeyEvent.VK_BACK_SPACE ||
						e.getKeyCode() == KeyEvent.VK_DELETE){
					SwingUtilities.invokeLater(new Runnable() {
						@Override
						public void run() {
							String text = numberField.getText();
							if(text.isEmpty()){
								numberField.setText("0");
								decButton.setEnabled(false);
								incButton.setEnabled(true);
								return;
							}
							if(Long.valueOf(text) <= 0){
								decButton.setEnabled(false);
								incButton.setEnabled(true);
							}else if(Long.valueOf(text) >= 10){
								incButton.setEnabled(false);
								decButton.setEnabled(true);
							}else{
								incButton.setEnabled(true);
								decButton.setEnabled(true);
							}
						}
					});
				}
			}
		});
		
		
		incButton.addActionListener(new ActionListener(){
			@Override
			public void actionPerformed(ActionEvent e) {
				String text = numberField.getText();
				numberField.setText((Long.valueOf(text) + 1) + "");
				if(Long.valueOf(text) + 1 >= 10){
					incButton.setEnabled(false);
				}
				
				if(Long.valueOf(text) + 1 > 0){
					decButton.setEnabled(true);
				}
			}
		});
		
		
		decButton.addActionListener(new ActionListener(){
			@Override
			public void actionPerformed(ActionEvent e) {
				String text = numberField.getText();
				numberField.setText((Long.valueOf(text) - 1) + "");
				if(Long.valueOf(text) - 1 <= 0){
					decButton.setEnabled(false);
				}
				
				if(Long.valueOf(text) - 1 < 10){
					incButton.setEnabled(true);
				}
			}
		});
		
		
		setLayout(new GridLayout(2, 1));
		
		
		JPanel buttonPanel = new JPanel();
		
		
		buttonPanel.setLayout(new GridLayout(1, 2));
		
		buttonPanel.add(incButton);
		buttonPanel.add(decButton);
		
		
		add(numberField);
		add(buttonPanel);
		
		pack();
		
	}

	public static void main(String[] args){
		new Interact().setVisible(true);
	}
}