Java 范例 - 只读集合
使用 Collection 类的 Collections.unmodifiableList() 方法来设置集合为只读
import java.util.ArrayList; import java.util.Arrays; import java.util.Collections; import java.util.HashMap; import java.util.HashSet; import java.util.List; import java.util.Map; import java.util.Set; public class Main { public static void main(String[] argv) throws Exception { List stuff = Arrays.asList(new String[] { "a", "b" }); List list = new ArrayList(stuff); list = Collections.unmodifiableList(list); try { list.set(0, "new value"); } catch (UnsupportedOperationException e) { } Set set = new HashSet(stuff); set = Collections.unmodifiableSet(set); Map map = new HashMap(); map = Collections.unmodifiableMap(map); System.out.println("集合现在是只读"); } }
编译运行以上 Java 代码,输出结果如下
集合现在是只读