变量Map的方法
//java 遍历map的四种方式
public static void main(String[] args) {
Map<String, String> map = new HashMap<String, String>();
("1", "value1");
("2", "value2");
("3", "value3");
//第一种：普遍使用，二次取值
("通过遍历key和value：");
for (String key : ()) {
("key= "+ key + " and value= " + (key));
}
//第二种：推荐，尤其是容量大时
("通过遍历key和value");
for (<String, String> entry : ()) {
("key= " + () + " and value= " + ());
}
//第三种
("通过使用iterator遍历key和value：");
Iterator<<String, String>> it = ().iterator();
while (()) {
<String, String> entry = ();
("key= " + () + " and value= " + ());
}
//第四种
("通过()遍历所有的value，但不能遍历key");
for (String v : ()) {
("value= " + v);
}
}