HashMap遍历方法

1.使用foreach循环遍历

Map hashMap = new HashMap();
hashMap.put("1", "good");
hashMap.put("2", "study");
hashMap.put("3", "day");
hashMap.put("4", "up");
for (Map.Entry entry : hashMap.entrySet()) {
    System.out.println(entry.getKey()+":"+entry.getValue());
}

2.使用foreach迭代键值对

Map hashMap = new HashMap();
hashMap.put("1", "good");
hashMap.put("2", "study");
hashMap.put("3", "day");
hashMap.put("4", "up");
for (String key : hashMap.keySet()) {
    System.out.println(key);
}
for (String value : hashMap.values()) {
    System.out.println(value);
}

3.使用迭代器

Map hashMap = new HashMap();
hashMap.put("1", "good");
hashMap.put("2", "study");
hashMap.put("3", "day");
hashMap.put("4", "up");

Iterator> iterator = hashMap.entrySet().iterator();
while (iterator.hasNext()) {
    Map.Entry next = iterator.next();
    System.out.println(next.getKey()+":"+next.getValue());
}

4.使用lambda表达式

Map hashMap = new HashMap();
hashMap.put("1", "good");
hashMap.put("2", "study");
hashMap.put("3", "day");
hashMap.put("4", "up");
hashMap.forEach((k,v)-> System.out.println(k+":"+v));