Java每日一题（3）

发布时间：2019-07-04 10:03:11编辑：auto阅读（2026）

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;
      }
    }
    
  }
}


 

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