JAVA如何随机取出Map中的一对键和值?

Question

如题所述

Answer 1

举个例子：

Map<Integer, String> map = new HashMap<Integer, String>();

先拿所有的键：

Integer[] keys = map.keySet().toArray(new Integer[0]);

然後随机一个键，找出该值：

Random random = new Random();

Integer randomKey = keys[random.nextInt(keys.length)];

String randomValue = map.get(randomKey);

//第一种：普遍使用，二次取值

System.out.println("通过Map.keySet遍历key和value：");

for (String key : map.keySet()) {

System.out.println("key= "+ key + " and value= " + map.get(key));

}

//第二种

System.out.println("通过Map.entrySet使用iterator遍历key和value：");

Iterator<Map.Entry<String, String>> it = map.entrySet().iterator();

while (it.hasNext()) {

Map.Entry<String, String> entry = it.next();

System.out.println("key= " + entry.getKey() + " and value= " + entry.getValue());
}

Answer 2

譬如说：
Map<Integer, String> map = new HashMap<Integer, String>();

先拿所有的键：
Integer[] keys = map.keySet().toArray(new Integer[0]);

然後随机一个键，找出该值：
Random random = new Random();
Integer randomKey = keys[random.nextInt(keys.length)];
String randomValue = map.get(randomKey);