letterrandom.java

是用来生成测试数据的类

package Random;

import java.util.Random;
/**
 *	LetterRandom类主要用于生成指定长度的大小写及数字混合的随机字符串． 
 * 	@author shif
 * */

class MyRandom {
	private int max;
	private int min;
	private int num;
	private int tmp;

	Random rMax = new Random();
	Random rMin = new Random();

	public MyRandom(int min, int max) {
		this.max = max;
		this.min = min;
	}

	public int getNum() {
		do {
			num = rMax.nextInt(max);
		} while (num < min);
		return num;
	}
	
} 

public class LetterRandom {
	public static void main(String[] args)
	{
		LetterRandom random=new LetterRandom();
		System.out.println(random.getMixString(20));
	}
	
	public String getMixString(int length)
	{
		String mixString;
		// 数字和大、小写字母分布的3个区域   
		MyRandom random1 = new MyRandom(48, 57);
		MyRandom random2 = new MyRandom(65, 90);
		MyRandom random3 = new MyRandom(97, 122);

		//   随机选择进入这三个区域   
		Random ranTmp = new Random();
		int tmp = 0;

		byte[] b = new byte[length];

		for (int i = 0; i < b.length; i++) {
			tmp = ranTmp.nextInt(3);
			switch (tmp) {
			case 0:
				b[i] = (byte) random1.getNum();
				break;
			case 1:
				b[i] = (byte) random2.getNum();
				break;
			case 2:
				b[i] = (byte) random3.getNum();
				break;
			}
		} 
		mixString = new String(b);
		return mixString;
	}
 
}