Math.random()取得0<=x<1的double类型。Random直接上代码:import java.util.ArrayList; import java.util.Collections; import java.util.HashSet; import java.util.List; import java.util.Random; import java.util.Set;/** * Random 类 * http://www.juheit.com */ public class StudyRandom{ public static void main(String[] args){
//创建随机的实例 Random r = new Random();
//产生随机整数 int ranInt = r.nextInt();
System.out.println("ranInt:" + ranInt);
//产生相同的随机序列 r = new Random(IRandomConstant.SEED);
for(int i = 0; i < 5; i ++){ System.out.println(r.nextInt()); }
//每次产生不同的随机序列 r = new Random(System.currentTimeMillis()); for(int i = 0; i < 5; i ++){ System.out.println(r.nextInt()); }
//产生指定范围内的随机数 r = new Random(); for(int i = 0; i < 5; i ++){ // System.out.println(r.nextInt(50));//50以内 System.out.println(r.nextInt(51) + 50);//50~100之间的随机数 }
getRandomMaxMinNum();
}
/** * 取出50~100之间的随机数,取出其中的最大数、第二大数和最小数、第二小数 */ public static void getRandomMaxMinNum(){
Random r = new Random();
//创建无序集合 Set<Integer> randomSet = new HashSet<Integer>(); for(int i = 0; i < 10; i ++){ randomSet.add(new Integer(r.nextInt(51) + 50)); } System.out.println("randomSet:" + randomSet);
//创建有序集合 List<Integer> randomList = new ArrayList<Integer>(); randomList.addAll(randomSet);
import java.util.Collections;
import java.util.HashSet;
import java.util.List;
import java.util.Random;
import java.util.Set;/**
* Random 类
* http://www.juheit.com
*/
public class StudyRandom{ public static void main(String[] args){
//创建随机的实例
Random r = new Random();
//产生随机整数
int ranInt = r.nextInt();
System.out.println("ranInt:" + ranInt);
//产生相同的随机序列
r = new Random(IRandomConstant.SEED);
for(int i = 0; i < 5; i ++){
System.out.println(r.nextInt());
}
//每次产生不同的随机序列
r = new Random(System.currentTimeMillis());
for(int i = 0; i < 5; i ++){
System.out.println(r.nextInt());
}
//产生指定范围内的随机数
r = new Random();
for(int i = 0; i < 5; i ++){
// System.out.println(r.nextInt(50));//50以内
System.out.println(r.nextInt(51) + 50);//50~100之间的随机数
}
getRandomMaxMinNum();
}
/**
* 取出50~100之间的随机数,取出其中的最大数、第二大数和最小数、第二小数
*/
public static void getRandomMaxMinNum(){
Random r = new Random();
//创建无序集合
Set<Integer> randomSet = new HashSet<Integer>();
for(int i = 0; i < 10; i ++){
randomSet.add(new Integer(r.nextInt(51) + 50));
}
System.out.println("randomSet:" + randomSet);
//创建有序集合
List<Integer> randomList = new ArrayList<Integer>();
randomList.addAll(randomSet);
//排序
Collections.sort(randomList);
if(randomList.size() >= 2){
System.out.println("MaxInt:" + randomList.get(randomList.size() - 1));
System.out.println("MaxSecInt:" + randomList.get(randomList.size() - 2));
System.out.println("MinSecInt:" + randomList.get(1));
System.out.println("MinInt:" + randomList.get(0));
}
}
}interface IRandomConstant{
/**
* 随机种子
*/
public static final Long SEED = 1000000L;
}