在Java编程中，如何使一个集合只读？
下面的例子展示了如何使用Collection类的Collections.unmodifiableList()方法使一个集合为只读。
package com.yiibai;
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 ReadonlyCollection {
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("Collection is read-only now.");
}
}
上述代码示例将产生以下结果。
Collection is read-only now.
