import java.util.Collections;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Set;
/*
* 产生50个10到50的随机数,用hashMap统计每个随机数出现的次数,并求这些随机数中的最大值和最小值
*/
public class Statistics
{
public static void main(String[] args)
{
HashMap<Integer, Integer> hashMap = new HashMap<Integer, Integer>();
for (int i = 0; i < 50; i++)
{
//产生50个10到50的随机数
int random=(int)Math.round(Math.random()*40+10);
Integer key = Integer.valueOf(random);
//使用hashMap统计每个随机数出现的次数,将随机数作为键,出现次数作为值
if (hashMap.get(key) == null)
{
hashMap.put(key, 1);
} else {
Integer value = (Integer)hashMap.get(key);
value = Integer.valueOf(value.intValue() + 1);
hashMap.put(key, value);
}
}
Set<Integer> keyIntegers = (Set<Integer>)hashMap.keySet();
for (Iterator<Integer> iterator = keyIntegers.iterator(); iterator.hasNext();)
{
Integer keyInteger = (Integer)iterator.next();
Integer valueInteger = (Integer)hashMap.get(keyInteger);
System.out.println(keyInteger + "的出现次数是:" + valueInteger);
}
System.out.println("随机数中的最大值是:" + Collections.max(keyIntegers));
System.out.println("随机数中的最小值是:" + Collections.min(keyIntegers));
}
}
import java.util.HashMap;
import java.util.Iterator;
import java.util.Set;
/**
* HashMap的应用,统计一个字符串中同一字符出现的字数
* @author c
*/
public class HashMapTest
{
public static void main(String[] args)
{
String s = "ajlsdfjhlahfuirhgjdnfafidofj";
char[] c = s.toCharArray();
HashMap<Character, Integer> map = new HashMap<Character, Integer>();
for (int i = 0; i < c.length; i++)
{
/*
* HaspMap的get方法如果不存在该键则返回null,如果存在则值(次数)加1
*/
if (map.get(Character.valueOf(c[i])) == null)
{
map.put(Character.valueOf(c[i]), 1);
} else {
Integer value = map.get(Character.valueOf(c[i]));
value = Integer.valueOf(value.intValue() + 1);
map.put(Character.valueOf(c[i]), value);
}
}
Set<Character> set = map.keySet();
Iterator<Character> iterator = set.iterator();
while (iterator.hasNext())
{
Character key = (Character)iterator.next();
Integer val = (Integer)map.get(key);
System.out.println("字符" + key + "的出现次数是:" + val);
}
}
}