hashmap有哪些遍历方式

有三种：① foreachmport java.io.IOException; import java.util.HashMap; import java.util.Map;

public class Test { public static void main(String[] args) throws IOException { Map<Integer, Integer> map = new HashMap<Integer, Integer>(); map.put(1, 10); map.put(2, 20);

	// Iterating entries using a For Each loop
	for (Map.Entry<Integer, Integer> entry : map.entrySet()) {
		System.out.println("Key = " + entry.getKey() + ", Value = " + entry.getValue());
	}

}

} ②迭代器 import java.io.IOException; import java.util.HashMap; import java.util.Iterator; import java.util.Map;

public class Test { public static void main(String[] args) throws IOException { Map<Integer, Integer> map = new HashMap<Integer, Integer>(); map.put(1, 10); map.put(2, 20);

	Iterator<Map.Entry<Integer, Integer>> entries = map.entrySet().iterator();
	while (entries.hasNext()) {
		Map.Entry<Integer, Integer> entry = entries.next();
		System.out.println("Key = " + entry.getKey() + ", Value = " + entry.getValue());
	}
}

} ③lambda表达式 import java.io.IOException; import java.util.HashMap; import java.util.Map;

public class Test {

public static void main(String[] args) throws IOException {

	Map<Integer, Integer> map = new HashMap<Integer, Integer>();
	map.put(1, 10);
	map.put(2, 20);
	map.forEach((k, v) -> System.out.println("key: " + k + " value:" + v));
}

}