Category Archives: Vs

Java: Arrays vs Collections


In Java, Arrays and Collections both are to  deal with group of objects but there are lots of differences in terms of  data structure or performing operations.

Here are some most common differences:

Difference between Arrays & Collections

Arrays Collections
Arrays is having fixed length.. Collections are growable in nature i.e increase or decrease.
Arrays are not recommended in terms of memory concerns. Collections use different data structure and recommended to use with respect to memory.
Arrays are use with respect to performance. Collections are not recommended to use with respect to performance.
Arrays can store only homogeneous (same type) of data. Collections can hold both homogeneous and heterogeneous elements.
Arrays do not have a single API. Collections having big list of methods.
Arrays can work with primitives and object types. Collections can hold only objects but not with primitive. If you pass as primitive internally convert to object.
See Also : Array & Arrays Class Examples See Also: Collection Framework and Examples
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Java : Non Primitive Data Types


Non-primitive data types are also called as reference types because they refer to objects.

Examples:  Strings, Arrays, Classes, Interface, etc. are non-primitive type.

Note: Non-primitive data type also called a User Defined Type when declaring an object with Classes and Interfaces names.

See Also: Java: Primitive Type Size and Default Value

Primitive Vs Non-Primitive

These are the main difference between primitive and non-primitive data types:

  • Primitive types are predefined in Java. While Non-primitive types are created by the programmer and is not defined by Java (except for String).
  • Non-primitive types also be used to call methods to perform certain operations, while primitive types cannot.
  • The primitive type has always had value, while non-primitive types can be null.
  • The primitive type starts with a lowercase letter, while non-primitive types start with an uppercase letter.
  • The primitive type size depends on the data type, while non-primitive types have all the same size.

Java: Difference between HashMap and Hashtable


HashMap and Hashtable both implements Map interface and used to store data in key and value pairs. Both use hashing techniques to get unique keys.

Apart from some similarities, there are many differences between HashMap and Hashtable classes as follows:

java.util.HashMap java.util.HashTable
HashMap class introduced in JDK 1.2. Hashtable is a legacy class.
HashMap inherits AbstractMap class. Hashtable inherits Dictionary class.
HashMap is traversed by Iterator. Hashtable is traversed by the Enumerator and Iterator.
Hashmap, Iterator is fail-fast. Hashtable, Enumerator is not fail-fast.
HashMap is not synchronized and not-thread safe. Hashtable is synchronized and thread safe.
HashMap can be synchronized by calling this code
Map m = Collections.synchronizedMap(hashMap);
Hashtable is internally synchronized and can’t be unsynchronized.
HashMap class allows only one null key and multiple null values. Hashtable doesn’t allow any null key or value.
HashMap is fast. Hashtable is slow.

For more detail:

 

JDBC : Difference between executeQuery() Vs executeUpdate() Vs execute() method


executeQuery(), executeUpdate() and execute() are the methods of java.sql.Statement interface of JDBC API which are used to execute the SQL statements.

executeQuery() Vs executeUpdate() Vs execute()

executeQuery() executeUpdate() execute()
This method is use to execute the SQL statements which retrieve some data from database. This statement is used to execute SQL statements which update or modify database. This method can be use for any kind of SQL statements.
This method returns a ResultSet object which contains the result returned by query. This method returns an int value which represent number of rows affected by the query. This will be 0 for statement which are returning nothing. This method return a Boolean value. TRUE indicates that query returned a ResultSet object and FALSE indicate returned an int value or returned nothing.
This method is use to execute select query. This method is use to execute non select query. This method is use to execute select and non select queries.
Ex: SELECT Ex:
DML->INSERT , UPDATE and DELETEDDL-> CREATE, ALTER
Any Type of SQL statements.

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Difference between Stored Procedure and functions


The differences between Stored procedures and Functions are given below:

See also :

Stored Procedure Function
Is used to perform business logic. Is used to perform calculation.
Must not have return type. Must have the return type.
May return zero or more values. May return only one values.
We can call function from procedure. Procedure can not be call from function.
Procedure supports input and output parameters Function supports only input parameters.
Exception handling using try/catch block can be used in stored procedures. Exception handling using try/catch can’t be used in user defined functions.

 

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JDBC: Difference between Statement, PreparedStatement and CallableSatement


JDBC API introduced statement, PreparedStatement and CallableStatemnet to execute different types of queries:

  1. Statement : Used to execute Normal SQL Queries.
  2. PreparedStatement: Used to execute dynamic or parameterized queries.
  3. CallableStatement: Used to execute StoredProcedure.

Statement Vs PreparedStatement Vs CallableStatement

Statement Prepared Statement Callable Statement
It is used to execute normal SQL queries. It is used to execute dynamic or parameterized SQL queries. It is used to execute Stored procedure or function.
It is proffered when particular query to be executed only once. It is proffered when particular query to be executed multiple times. It is proffered when stored procedure or functions to be executed.
You can no pass parameter to query by using this interface. You can pass parameter to query at run time by using this interface. You can pass three types of parameters by using this interface IN, OUT and IN OUT
This interface mainly used for DDL statements like CREATE, ALTER , DROP etc. This is used to be any kind of SQL queries which are used multiple times It is used with Stored Procedure and functions.
The performance of this interface is very low. The performance of this interface is better than query while using with multiple queries. Performance of this interface is very high because stored procedure execute on database end.
For More: Statement For More: Prepared Statement For More: Callable Interface

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