Java 對Map
做迴圈(loop)的寫法如下。
import java.util.HashMap;
import java.util.Map;
import java.util.Map.Entry;
public class Main {
public static void main(String[] args) {
Map<Integer, String> map = createMap();
// loop key
for (Integer key : map.keySet()) {
System.out.println(key);
}
printline();
// loop value
for (String value : map.values()) {
System.out.println(value);
}
printline();
// loop key:value
for (Integer key : map.keySet()) {
System.out.println(key + ":" + map.get(key));
}
printline();
// loop key:value <-- 常用
for (Entry<Integer, String> e : map.entrySet()) {
System.out.println(e.getKey() + ":" + e.getValue());
}
printline();
// Java 8 lambda expressoin
map.forEach((key, value) -> System.out.println(key + ":" + value));
}
/** 建立一個Map物件,塞一些資料 */
private static Map<Integer, String> createMap() {
Map<Integer, String> map = new HashMap<>();
map.put(1, "Matt");
map.put(2, "John");
map.put(3, "Terry");
map.put(4, "Mary");
map.put(5, "Amy");
return map;
}
/** 劃線 */
private static void printline() {
System.out.println("========================");
}
}
印出結果如下。
1
2
3
4
5
========================
Matt
John
Terry
Mary
Amy
========================
1:Matt
2:John
3:Terry
4:Mary
5:Amy
========================
1:Matt
2:John
3:Terry
4:Mary
5:Amy
========================
1:Matt
2:John
3:Terry
4:Mary
5:Amy
參考:
沒有留言:
張貼留言