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Toggle the table of contents. Java Excel API. Add languages. ... Java Excel API (a.k.a. JXL API) ... (String strSheetName, int iColumnNumber, int iRowNumber, String ...
Each table can have multiple unique constraints. On some RDBMS a unique constraint generates a nonclustered index by default. Note that unlike the PRIMARY KEY constraint a UNIQUE constraint does not imply NOT NULL for the columns participating in the constraint. NOT NULL must be specified to make the column(s) a key.
A requirement of E. F. Codd in his seminal paper is that a primary key of an entity, or any part of it, can never take a null value. [1] The relational model states that every relation (or table ) must have an identifier, called the primary key (abbreviated PK), in such a way that every row of the same relation be identifiable by its content ...
Nullable types are a feature of some programming languages which allow a value to be set to the special value NULL instead of the usual possible values of the data type.In statically typed languages, a nullable type is an option type, [citation needed] while in dynamically typed languages (where values have types, but variables do not), equivalent behavior is provided by having a single null ...
This is a list of the instructions that make up the Java bytecode, an abstract machine language that is ultimately executed by the Java virtual machine. [1] The Java bytecode is generated from languages running on the Java Platform, most notably the Java programming language.
A snippet of Java code with keywords highlighted in bold blue font. The syntax of Java is the set of rules defining how a Java program is written and interpreted. The syntax is mostly derived from C and C++. Unlike C++, Java has no global functions or variables, but has data members which are also regarded as global variables.
The Java type system, however, treats enumerations as a type separate from integers, and intermixing of enum and integer values is not allowed. In fact, an enum type in Java is actually a special compiler-generated class rather than an arithmetic type, and enum values behave as global pre-generated instances of that class. Enum types can have ...
Collections can grow and shrink in size automatically when objects are added or removed. Collections cannot hold primitive data types such as int, long, or double. [2] Instead, Collections can hold wrapper classes such as java.lang.Integer, java.lang.Long, or java.lang.Double. [3] Collections are generic and hence invariant, but arrays are ...