Set接口:无序集合,不允许有重复值,允许有null值 存入与取出的顺序有可能不一致 HashSet:具有set集合的基本特性,不允许重复值,允许null值 底层实现是哈希表结构 初始容量为16 保存自定义对象时,保证数据的唯一性,主要由哈希表的结构决定 先判断hashCode()是否相同,若相同,再判断equals()是否相同 哈希表结构:哈希表...
// 添加元素到 LinkedHashSet,包括 nulllinkedHashSet.add("Apple");linkedHashSet.add("Banana");linkedHashSet.add(null);// 添加 null 值linkedHashSet.add("Cherry");// 打印 LinkedHashSet 的内容System.out.println("LinkedHashSet 中的元素:"+linkedHashSet);// 检查 LinkedHashSet 是否包含 nullif(...
Namespace: Java.Sql Assembly: Mono.Android.dll The constant indicating that a column allows NULL values. [Android.Runtime.Register("columnNullable")] public const int ColumnNullable = 1; Field Value Value = 1 Int32 Attributes RegisterAttribute Remarks The constant indicating that a column ...
set.add(null); System.out.println("HashSet :"+set.size());//1Set linkedHashSet=newLinkedHashSet(); linkedHashSet.add(null); linkedHashSet.add(null); System.out.println("LinkedHashSet :"+linkedHashSet.size());//1Set treeSet=newTreeSet();//treeSet.add(null);//treeSet key不能nu...
Returns: An instance of DiskEncryptionSetInner if the JsonReader was pointing to an instance of it, or null if it was pointing to JSON null. Throws: IOException - If the deserialized JSON object was missing any required properties. id...
The constant indicating that a column allowsNULLvalues. Java documentation forjava.sql.ResultSetMetaData.columnNullable. Portions of this page are modifications based on work created and shared by theAndroid Open Source Projectand used according to terms described in theCreative Commons 2.5 Attribution ...
The constant indicating that a column allowsNULLvalues. Java documentation forjava.sql.ResultSetMetaData.columnNullable. Portions of this page are modifications based on work created and shared by theAndroid Open Source Projectand used according to terms described in theCreative Commons 2.5 Attribution ...
The values ResultSet.FETCH_REVERSE and ResultSet.FETCH_UNKNOWN are not supported--attempting to specify them causes a SQL warning, and the settings are ignored. Updating Result SetsA concurrency type of CONCUR_UPDATABLE allows you to update rows in the result set, delete rows from the result ...
java: INSERTINTOEXAMPLE(product,service,itf,latency)VALUES('p1','s1','i1',null); expected result: productserviceitflatency p1s1i1infinity but i got: productserviceitflatency p1s1i10 I try to set the connection propertynullAsDefault to 0 or 1 or 2, they all doesn't work! (jdbc version...
在ssh 项目中 如果某个实体类 的字段属性为 基本数据类型,那么要注意对应的数据库中该属性 值不能为null 否则,在做相关查询时 会报该异常,具体的原理就是:hibernate 通过实体bean的set 为实体ben属性赋值