可以用数组或者链表实现一个编辑器的功能，各自有各自的优缺点。
这里只实现了单行的输入、删除、左移、右移功能，可以加入换行符实现多行文本编辑功能（但是链表实现这个不是很好设计，十字链表？这个最好还是使用数组），还可以加入文件的读取和存储实现编辑器的打开和保存功能，还可以加入网络连接实现编辑器的网络同步和备份功能。
//ZJSNote.java:
package com.zhuojiaoshou;

import javax.swing.*;
import java.awt.*;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;

/**
 * Created by JiajieZhuo on 2017/3/5.
 */
public class ZJSNote {
    public static void main(String[] args) {
        JFrame jFrame = new JFrame();
        jFrame.setSize(300, 400);

        MyPanel mp = new MyPanel();
        jFrame.add(mp);

        jFrame.addKeyListener(mp);
        mp.addKeyListener(mp);

        jFrame.setVisible(true);
    }
}

class Node {
    public char value = ' ';
    public Node next = null;
}

class MyPanel extends JPanel implements KeyListener {
    Node firstNode = new Node();
    Node nowNode = firstNode;
    int cursor = 0;

    @Override
    public void paint(Graphics g) {
        // clear screen
        super.paint(g);

        Node tmpNode = firstNode;
        int x = 0;

        // word
        while (tmpNode.next != null) {
            g.drawString("" + tmpNode.next.value, 10 + x * 8, 10);
            x++;
            tmpNode = tmpNode.next;
        }

        // cursor
        g.drawLine(10 + cursor * 8, 0, 10 + cursor * 8, 10);
    }

    @Override
    public void keyTyped(KeyEvent e) {

    }

    @Override
    public void keyPressed(KeyEvent e) {
        if (e.getKeyCode() >= KeyEvent.VK_A && e.getKeyCode() <= KeyEvent.VK_Z) {
            if (nowNode.next == null) {
                Node newNode = new Node();
                newNode.value = e.getKeyChar();
                nowNode.next = newNode;
                nowNode = newNode;
                cursor++;
            } else {
                Node newNode = new Node();
                newNode.value = e.getKeyChar();
                newNode.next = nowNode.next;
                nowNode.next = newNode;
                nowNode = newNode;
                cursor++;
            }
        }
        if (e.getKeyCode() == KeyEvent.VK_DELETE) {
            if (nowNode.next != null) {
                nowNode.next = nowNode.next.next;
                cursor--;
            }
        }
        if (e.getKeyCode() == KeyEvent.VK_BACK_SPACE) {
            if (cursor > 0) {
                Node tmpNode = firstNode;
                while (tmpNode.next != nowNode) {
                    tmpNode = tmpNode.next;
                }
                tmpNode.next = nowNode.next;
                nowNode = tmpNode;
                cursor--;
            }
        }
        if (e.getKeyCode() == KeyEvent.VK_LEFT) {
            if (cursor > 0) {
                cursor--;
                Node tmpNode = firstNode;
                while (tmpNode.next != nowNode) {
                    tmpNode = tmpNode.next;
                }
                nowNode = tmpNode;
            }
        }
        if (e.getKeyCode() == KeyEvent.VK_RIGHT) {
            if (nowNode.next != null) {
                cursor++;
                nowNode = nowNode.next;
            }
        }

        repaint();
    }

    @Override
    public void keyReleased(KeyEvent e) {

    }
}