Android中利用Random生成随机数

MainActivity如下:

package cc.test;

import java.util.HashSet;
import java.util.Random;
import android.app.Activity;
import android.os.Bundle;
/**
 * 
 * Demo描述:
 * Java中利用Random生成随机数
 * 
 * 参考资料:
 * 1 http://blog.csdn.net/herrapfel/article/details/1885016
 * 2 http://blog.csdn.net/yuxuepiaoguo/article/details/4195198
 * 3 http://blog.csdn.net/zhongyili_sohu/article/details/7906125
 * 4 http://www.csdn.net/article/2012-03-22/313407
 *   Thank you very much
 */
public class TestRandomActivity extends Activity {
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        testRandom1();
        testRandom2();
        testRandom3();
    }
    
    
    
    //生成随机数
    private void testRandom1(){
    	Random random=new Random();
    	for (int i = 0; i <5; i++) {
			System.out.println("random.nextInt()="+random.nextInt());
		}
    	System.out.println("/////以上为testRandom1()的测试///////");
    }
    
    
    
    //在一定范围内生成随机数.
    //比如此处要求在[0 - n)内生成随机数.
    //注意:包含0不包含n
    private void testRandom2(){
    	Random random=new Random();
    	for (int i = 0; i <10; i++) {
			System.out.println("random.nextInt()="+random.nextInt(20));
		}
    	System.out.println("/////以上为testRandom2()的测试///////");
    }
    
    
    //在一定范围内生成不重复的随机数
    //在testRandom2中生成的随机数可能会重复.
    //在此处避免该问题
    private void testRandom3(){
    	HashSet integerHashSet=new HashSet();
    	Random random=new Random();
    	for (int i = 0; i <10; i++) {
    		int randomInt=random.nextInt(20);
    		System.out.println("生成的randomInt="+randomInt);
    		if (!integerHashSet.contains(randomInt)) {
    			integerHashSet.add(randomInt);
    			System.out.println("添加进HashSet的randomInt="+randomInt);
			}else {
				System.out.println("该数字已经被添加,不能重复添加");
			}
		}
    	System.out.println("/////以上为testRandom3()的测试///////");
    }
    
}