编程实现，创建两个线程，两个线程都循环输出10次，每次输出一行。一个线程输出0~9的随机数，每行输出10个；另一个线程输出字母a~z，每行输出26个。

在Java中，我们可以使用`Thread`类和`synchronized`关键字来实现这个场景。下面是一个简单的示例，展示了如何创建两个线程，分别输出数字和字母：

import java.util.Random;
import java.util.concurrent.atomic.AtomicInteger;

public class MultiThreadExample {
    private static final AtomicInteger lineCounter = new AtomicInteger(0);
    private static final int MAX_LINES = 10;
    private static final int NUM_DIGITS = 10;
    private static final char[] ALPHABET = 'a' - 'A' + '0';

    public static void main(String[] args) {
        Thread randomThread = new Thread(() -> printRandomNumbers());
        Thread alphabetThread = new Thread(() -> printAlphabet());

        randomThread.start();
        alphabetThread.start();

        try {
            randomThread.join(); // 等待randomThread完成
            alphabetThread.join(); // 然后再等待alphabetThread完成
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }

    private static synchronized void printRandomNumbers() {
        while (lineCounter.getAndIncrement() < MAX_LINES) {
            System.out.println(getRandomLine(NUM_DIGITS));
        }
    }

    private static synchronized void printAlphabet() {
        while (lineCounter.getAndIncrement() < MAX_LINES) {
            System.out.println(getAlphabetLine());
        }
    }

    private static String getRandomLine(int numDigits) {
        Random random = new Random();
        StringBuilder line = new StringBuilder();
        for (int i = 0; i < 10; i++) {
            line.append(random.nextInt(NUM_DIGITS)).append(' ');
        }
        return line.toString();
    }

    private static String getAlphabetLine() {
        StringBuilder line = new StringBuilder();
        for (char c : ALPHABET) {
            if (line.length() == 26) {
                break;
            }
            line.append(c);
        }
        return line.toString();
    }
}