Java 實(shí)例 - 只讀集合
以下實(shí)例演示了如何使用 Collection 類的 Collections.unmodifiableList() 方法來設(shè)置集合為只讀:
/* author by w3cschool.cc Main.java */ 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("集合現(xiàn)在是只讀"); } }
以上代碼運(yùn)行輸出結(jié)果為:
集合現(xiàn)在是只讀
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