Java每日一题（3）

题目：

使用java.lang.Math类，生成100个0到99之间的随机整数，找出它们之中的最大者和最小者，并统计大于50的整数个数

已有答案：

http://jythoner.javaeye.com/blog/322336?page=1#comments

另答：

/** *     */ package math; import java.util.ArrayList; import java.util.Collections; import java.util.Comparator; import java.util.Random; /** * @author daniel zhou * */ public class RandomTest { /**     * Create 100 random numbers, get min & max number, sun up the number of >50     * @param args     */ public static void main(String[] args) { /**      * Here main show how to create an random number in some scope     // get random by java.lang.Math     double random = Math.random()*100;     int in=(int) random;         System.out.println(random);     System.out.println(in);     // get random by java.util.Random     Random ra=new Random();     System.out.println(ra.nextInt(100));     **/ //create 100 random number     ArrayList<Integer> arraylist=new ArrayList<Integer>();     Random rand=new Random(); int total_50=0; for (int i = 0; i < 100; i++) { int num=rand.nextInt(100);       arraylist.add(Integer.valueOf(num)); //get number of >50 if(num>50)total_50++;     }     System.out.println("numbers of >50 is: "+total_50); //sort the arraylist     Comparator<Integer> comp=new MyComparator();     Collections.sort(arraylist, comp); //out min & max     System.out.println("Min number is: "+arraylist.get(0));     System.out.println("Max number is: "+arraylist.get(99));   } }

Comparator：

package math; import java.util.Comparator; /** *     * @author daniel zhou * */ public class MyComparator implements Comparator<Integer>{   @Override public int compare(final Integer o1, final Integer o2) { final Integer x=(Integer)o1; final Integer y=(Integer)o2; if (x>y) { return 1;     }else{ return 0;     }   } }

或者将比较器写为一个内部类也是可以的，代码如下：

/** *     */ package math; import java.util.ArrayList; import java.util.Collections; import java.util.Comparator; import java.util.Random; /** * @author daniel zhou * */ public class RandomTest { /**     * Create 100 random numbers, get min & max number, sun up the number of >50     * @param args     */ public static void main(String[] args) { //create 100 random number     ArrayList<Integer> arraylist=new ArrayList<Integer>();     Random rand=new Random(); int total_50=0; for (int i = 0; i < 100; i++) { int num=rand.nextInt(100);       arraylist.add(Integer.valueOf(num)); //get number of >50 if(num>50)total_50++;     }     System.out.println("numbers of >50 is: "+total_50); //sort the arraylist     Comparator<Integer> comp=new MyComparator();     Collections.sort(arraylist, comp); //out min & max     System.out.println("Min number is: "+arraylist.get(0));     System.out.println("Max number is: "+arraylist.get(99));   } public static class MyComparator implements Comparator<Integer>{     @Override public int compare(final Integer o1, final Integer o2) { final Integer x=(Integer)o1; final Integer y=(Integer)o2; if (x>y) { return 1;       }else{ return 0;       }     }   } }