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JShell is an interactive Java Shell tool that enables us to execute java code from the shell and instantly displays the output. JShell is the REPL(Read Evaluate Print Loop) tool that runs from the command-line. We can start a JShell by simply typing "jshell" in the command prompt, and to exit the jshell by using "/exit" command. For small snippets, we do not need to create a main() method in JShell.We can also implement the major collections like list, map and set by using this tool. In the below program, we can implement an ArrayList with various scenarios.ExampleC:\Users\User\Desktop\Java 9 QNA>jshell | Welcome to JShell ... Read More
In Java 9, Platform Logging API can be used to log messages with a service interface for consumers of those messages. An implementation of LoggerFinder has been loaded with the help of java.util.ServiceLoader API by using System ClassLoader. Based on this implementation, an application can plug in its own external logging backend without configuring java.util.logging.We can pass a class name or module to LoggerFinder so that it knows which logger to return.public class MyLoggerFinder extends LoggerFinder { @Override public Logger getLogger(String name, Module module) { // return a logger depends on name/module } }If no concrete implementation can be found, then ... Read More
StackWalker API provides a stream of information in stack traces during the execution of a program. This API requires a virtual machine to capture a snapshot of the entire stack and returns an array of elements for filtering purposes. We need to skip, drop, and limit the stack frames by using the walk() method. We can also filter a stack frame by class for getting the first matching frame, and all matching frames by using the filter() method.In the below example, we can filter a stack frame by using StackWalker API.Exampleimport java.lang.StackWalker.StackFrame; import java.util.*; import java.util.stream.*; public class StackWalkerFilterTest { ... Read More
Java 9 defines a StackWalker API that provides laziness and frame filtering. An object of StackWalker allows us to traverse and access stacks and contains one useful method: walk(). This method opens a StackFrame stream for the current thread, then applies the function with that StackFrame stream. We need to get StackWalker object, then use StackWalker.getInstance() method.In the below example, we can print different stack frames: all stack frames, skip some stack frames and limit stack frames by using StackWalker API.Exampleimport java.lang.StackWalker.StackFrame; import java.util.*; import java.util.stream.*; public class StackWalkerTest { public static void main(String args[]) { new StackWalkerTest().walk(); } private void walk() { ... Read More
Since Java 9, we can create Reactive Streams by introducing four core interfaces: Publisher, Subscriber, Subscription, Processor, and one concrete class: SubmissionPublisher that implements the Publisher interface. Each interface plays a different role, corresponding to the principles of Reactive Streams. We can use the submit() method of SubmissionPublisher class to publish the provided item to each subscriber.Syntaxpublic class SubmissionPublisher extends Object implements Flow.Publisher, AutoCloseableIn the below example, we can implement the SubmissionPublisher classExampleimport java.util.concurrent.Flow.Subscriber; import java.util.concurrent.Flow.Subscription; import java.util.concurrent.SubmissionPublisher; class MySubscriber implements Subscriber { private Subscription subscription; private String name; public MySubscriber(String name) { this.name = name; ... Read More
For this, use REPLACE() function and replace empty space with the character. Let us first create a table −mysql> create table DemoTable (Subject text); Query OK, 0 rows affected (0.86 sec)ExampleInsert some records in the table using insert command −mysql> insert into DemoTable values('Introduction to MySQL'); Query OK, 1 row affected (0.15 sec) mysql> insert into DemoTable values('Java in depth'); Query OK, 1 row affected (0.21 sec) mysql> insert into DemoTable values('Data Structure and Algorithm'); Query OK, 1 row affected (0.16 sec)Display all records from the table using select statement −mysql> select *from DemoTable;Output+------------------------------+ | Subject | +------------------------------+ | Introduction ... Read More
You can use INFORMATION_SCHEMA.COLUMNS table to display MySQL table name with columns. The syntax is as follows −SELECT DISTINCT TABLE_NAME, Column_Name FROM INFORMATION_SCHEMA.COLUMNS WHERE TABLE_SCHEMA = 'yourDatabaseName';Here, we have a database with the name ‘sample’ with tables. The query is as follows to display table name along with column name −mysql> SELECT DISTINCT TABLE_NAME, Column_Name -> FROM INFORMATION_SCHEMA.COLUMNS -> WHERE TABLE_SCHEMA = 'sample';Output+--------------------------------+-------------------------------+ | TABLE_NAME | COLUMN_NAME | +--------------------------------+-------------------------------+ | aggregatefunctiondemo | UserId ... Read More
Following are the differences between RowSet and ResultSet:ResultSetRowSetA ResultSet always maintains connection with the database.A RowSet can be connected, disconnected from the database.It cannot be serialized.A RowSet object can be serialized.ResultSet object cannot be passed other over network.You can pass a RowSet object over the network.ResultSet object is not a JavaBean objectYou can create/get a result set using the executeQuery() method.ResultSet Object is a JavaBean object.You can get a RowSet using the RowSetProvider.newFactory().createJdb cRowSet() method.By default, ResultSet object is not scrollable or, updatable.By default, RowSet object is scrollable and updatable.Read More
You can call the SQL stored procedures using the CallableStatement interface. A Callable statement can have input parameters, output parameters, or both.You can create an object of the CallableStatement (interface) using the prepareCall() method of the Connection interface. This method accepts a string variable representing a query to call the stored procedures and returns a CallableStatement object.Suppose you have a procedure name myProcedure in the database you can prepare a callable statement as://Preparing a CallableStatement CallableStatement cstmt = con.prepareCall("{call myProcedure(?, ?, ?)}");Then you can set values to the place holders using the setter methods of the CallableStatement interface and execute ... Read More
Java 9 has introduced Reactive Streams under java.util.concurrent.Flow package that supports an interoperable publish-subscribe framework. It processes an asynchronous stream of data across the asynchronous boundary (passing elements into another thread or thread-pool), and the receiving side is not forced to buffer arbitrary amounts of data, then buffer overflow can't occur.Flow API contains four interrelated core interfaces: Publisher, Subscriber, Subscription, and Processor.Syntax@FunctionalInterface public static interface Publisher { public void subscribe(Subscriber