java for遍历hashmap_Java 使用for和while循环遍历HashMap的方法及示例代码
1､使用entrySet()遍历
1) 使用while实现public static void printMap(Map mp) {
Iterator it = mp.entrySet().iterator();
while (it.hasNext()) {
Map.Entry pair = (Map.Entry)it.next();
System.out.println(pair.getKey() + " = " + pair.getValue());
it.remove(); // avoids a ConcurrentModificationException
}
}
2) 使用for实现for (Map.Entry entry : map.entrySet()) {
String key = entry.getKey();
Object value = entry.getValue();
// ...
}
2､使用for和keySet()或values()实现
相关文档：
1) 使用keySet()遍历keyCollection> keys = map.keySet();
for(Object key: keys){
System.out.println("Key " + key);
System.out.println("Value " + map.get(key));
}
2)使用values()遍历值Map map = new HashMap();
for (Integer value : map.values()) {
System.out.println("Value = " + value);
}
3､HashMap使用示例代码import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map.Entry;
public class HashMapTest {
public static void main(String[] args) {
HashMap map = new HashMap<>();
map.put("java", "31");//存放键值对
System.out.println(map.containsKey("java"));//键中是否包含这个数据
System.out.println(map.containsKey("python"));
System.out.println("=========================");
System.out.println(map.get("java"));//通过键拿值
System.out.println(map.get("python"));
System.out.println("=========================");
System.out.println(map.isEmpty());//判空
System.out.println(map.size());
System.out.println("=========================");
System.out.println(map.remove("java"));//从键值中删除
System.out.println(map.containsKey("python"));
System.out.println(map.get("javapy"));//获取值
System.out.println(map.isEmpty());
System.out.println(map.size());
System.out.println("=========================");
map.put("cjavapy", "31");
System.out.println(map.get("cjavapy"));
map.put("cjavapy", "32");
System.out.println(map.get("cjavapy"));
System.out.println("=========================");
map.put("cjavapy", "1");
map.put("javapy", "2");
map.put("python", "3");
for (String key : map.keySet()) {
System.out.println(key);
}
System.out.println("=========================");
for (String values : map.values()) {
System.out.println(values);
}
System.out.println("=========================");
map.clear();
map.put("A", "1");
map.put("B", "2");
map.put("C", "3");
map.put("D", "1");
map.put("E", "2");
map.put("F", "3");
map.put("G", "1");
map.put("H", "2");
map.put("I", "3");
for (Entry entry : map.entrySet()) {
String key = entry.getKey();
String value = entry.getValue();
System.out.println(key + "," + value);
}
System.out.println("=========================");
List removeKeys = new ArrayList();
for (Entry entry : map.entrySet()) {
if (!entry.getValue().equals("1")) {
removeKeys.add(entry.getKey());
}
}
for (String removeKey : removeKeys) {
map.remove(removeKey);
}
for (Entry entry : map.entrySet()) {
String key = entry.getKey();
String value = entry.getValue();
System.out.println(key + "," + value);
}
System.out.println("=========================");
}
}
相关文档：