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In data structure, Linked List is a linear collection of data elements. Each element or node of a list is comprising of two items - the data and a reference to the next node. The last node has a reference to null. Into a linked list the entry point is called the head of the list.Each node in the list stores the contents and a pointer or reference to the next node in the list, in a singly linked list. Singly linked list does not store any pointer or reference to the previous node.As it is a sorted singly linked ... Read More
Following is the syntax to return only a single property _id in MongoDBdb.yourCollectionName.find({}, {"_id": 1}).pretty();Let us first create a collection with documents> db.singlePropertyIdDemo.insertOne({"_id":101, "UserName":"Larry", "UserAge":21}); { "acknowledged" : true, "insertedId" : 101 } > db.singlePropertyIdDemo.insertOne({"_id":102, "UserName":"Mike", "UserAge":26}); { "acknowledged" : true, "insertedId" : 102 } > db.singlePropertyIdDemo.insertOne({"_id":103, "UserName":"Chris", "UserAge":24}); { "acknowledged" : true, "insertedId" : 103 } > db.singlePropertyIdDemo.insertOne({"_id":104, "UserName":"Robert", "UserAge":23}); { "acknowledged" : true, "insertedId" : 104 } > db.singlePropertyIdDemo.insertOne({"_id":105, "UserName":"John", "UserAge":27}); { "acknowledged" : true, "insertedId" : 105 }Following is the query to display all documents from a collection with the help of find() method> db.singlePropertyIdDemo.find().pretty();This will produce ... Read More
To evaluate mathematical expression in String, use Nashorn JavaScript in Java i.e. scripting. Nashorn invoke dynamics feature, introduced in Java 7 to improve performance.For scripting, use the ScriptEngineManager class for the engine −ScriptEngineManager scriptEngineManager = new ScriptEngineManager(); ScriptEngine scriptEngine = scriptEngineManager.getEngineByName("JavaScript");Now for JavaScript code from string, use eval i.e. execute the script. Here, we are evaluating mathematical expressions in a string −Object ob = scriptEngine.eval("9 + 15 + 30"); System.out.println("Result of evaluating mathematical expressions in String = "+ob);Example Live Demoimport javax.script.ScriptEngine; import javax.script.ScriptEngineManager; public class Main { public static void main(String[] args) throws Exception { ScriptEngineManager scriptEngineManager ... Read More
For this, you can use SUBSTR along with length().Let us first create a table −mysql> create table DemoTable ( Id int NOT NULL AUTO_INCREMENT PRIMARY KEY, FirstName varchar(20) ); Query OK, 0 rows affected (1.31 sec)Following is the query to insert some records in the table using insert command −mysql> insert into DemoTable(FirstName) values('John'); Query OK, 1 row affected (0.14 sec) mysql> insert into DemoTable(FirstName) values('Carol'); Query OK, 1 row affected (0.22 sec) mysql> insert into DemoTable(FirstName) values('Robert'); Query OK, 1 row affected (0.14 sec) mysql> insert into DemoTable(FirstName) values('Chris'); Query OK, 1 row affected (0.16 ... Read More
You can use the concept of toArray() to create array. Following is the syntax −db.yourCollectonName.find({}, {yourFieldName:1}).toArray();Let us create a collection with documents −> db.createArrayDemo.insertOne({"UserName":"Chris"}); { "acknowledged" : true, "insertedId" : ObjectId("5cbd6461de8cc557214c0e00") } > db.createArrayDemo.insertOne({"UserName":"David"}); { "acknowledged" : true, "insertedId" : ObjectId("5cbd6467de8cc557214c0e01") } > db.createArrayDemo.insertOne({"UserName":"Robert"}); { "acknowledged" : true, "insertedId" : ObjectId("5cbd646cde8cc557214c0e02") } > db.createArrayDemo.insertOne({"UserName":"Sam"}); { "acknowledged" : true, "insertedId" : ObjectId("5cbd6470de8cc557214c0e03") }Display all documents from a collection with the help of find() method −> db.createArrayDemo.find().pretty();This will produce the following output −{ "_id" : ObjectId("5cbd6461de8cc557214c0e00"), "UserName" : "Chris" } { "_id" : ObjectId("5cbd6467de8cc557214c0e01"), ... Read More
There is no equivalent of ROW_NUMBER() in MySQL for inserting but you can achieve this with the help of variable. The syntax is as follows −SELECT (@yourVariableName:=@yourVariableName + 1) AS `anyAliasName`, yourColumnName1, yourColumnName2, ...N FROM yourTableName ,(SELECT @yourVariableName:=0) AS anyAliasName;To understand the above syntax, let us create a table. The query to create a table is as follows −mysql> create table RowNumberDemo -> ( -> UserId int, -> UserName varchar(20) -> ); Query OK, 0 rows affected (0.74 sec)Insert some records in the table using insert command. The ... Read More
An immutable copy of a duration where some milliseconds are removed from it can be obtained using the minusMillis() method in the Duration class in Java. This method requires a single parameter i.e. the number of milliseconds to be subtracted and it returns the duration with the subtracted milliseconds.A program that demonstrates this is given as follows −Example Live Demoimport java.time.Duration; public class Demo { public static void main(String[] args) { Duration d = Duration.ofSeconds(1); System.out.println("The duration is: " + d); ... Read More
You can use UNION to get the previous and next record in MySQL.The syntax is as follows(select *from yourTableName WHERE yourIdColumnName > yourValue ORDER BY yourIdColumnName ASC LIMIT 1) UNION (select *from yourTableName WHERE yourIdColumnName < yourValue ORDER BY yourIdColumnName DESC LIMIT 1);To understand the concept, let us create a table. The query to create a table is as followsmysql> create table previousAndNextRecordDemo - > ( - > Id int NOT NULL AUTO_INCREMENT PRIMARY KEY, - > Name varchar(30) - > ); Query OK, 0 rows affected (1.04 ... Read More
The range of values for a field can be obtained using the range() method in the Instant class in Java. This method requires a single parameter i.e. the ChronoField for which the range of values are required and it returns the range of valid values for the ChronoField.A program that demonstrates this is given as follows −Example Live Demoimport java.time.*; import java.time.temporal.ChronoField; import java.time.temporal.ValueRange; public class Demo { public static void main(String[] args) { Instant i = Instant.now(); ValueRange range1 = i.range(ChronoField.MILLI_OF_SECOND); ... Read More
The toList() method of the Collectors class returns a Collector that accumulates the input elements into a new List.The syntax is as follows −static Collector toList()Here, parameter T is the type of input elements.To work with Collectors class in Java, import the following package −import java.util.stream.Collectors;The following is an example to implement Collectors toList() method in Java −Example Live Demoimport java.util.List; import java.util.stream.Collectors; import java.util.stream.Stream; public class Demo { public static void main(String[] args) { Stream stream = Stream.of("25", "40", "90", "150", "180", "220", "350"); ... Read More