Java程序将Map转换为只读Map
假设以下是我们的映射-
Map<String, String>map = new HashMap<String,String>();
map.put("1","A");
map.put("2","B");
map.put("3","C");使用unmodifiableMap()方法将其设为只读-
map = Collections.unmodifiableMap(map);
示例
import java.util.Collections;
import java.util.HashMap;
import java.util.Map;
public class Demo {
public static void main(String[] argv) throws Exception {
Map<String, String>map = new HashMap<String,String>();
map.put("1","A");
map.put("2","B");
map.put("3","C");
//将其设为只读
map = Collections.unmodifiableMap(map);
try {
map.put("4","D");
map.put("5","E");
map.put("6","F");
} catch (UnsupportedOperationException e) {
System.out.println(e.getMessage());
}
}
}输出结果
null