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    <blockquote> <p>What is the best way in Java to create a singleton?</p> </blockquote> <p>Follow the design pattern creation guidelines. i.e private constructor, etc.</p> <blockquote> <p>Should a DB connection be a singleton (being a singleton it's automatically thread-safe)?</p> </blockquote> <p>creating a DB connection as a singleton might be a poor design choice in many scenarios. Use it only if you are sure that you don't need DB concurrency. If you have multiple users logged in at the same time, or even if your single user spawns many threads that need to access the DB, then a DB Connection pool is a better choice. You can use either apache or tomcat db connection pools. THese classes are defined for example in the package</p> <pre><code>org.apache.commons.dbcp.*; org.apache.tomcat.dbcp.dbcp.*; </code></pre> <p>where dbcp stands for database connection pooling.</p> <p>The biggest reason for using a connection pool is that on average the time it takes for the DB access (DML etc) is much smaller than the time it takes to create a connection and then close the connection. Additionally, don't forget to close your ResultSet, PreparedStatement and Connection variables after the transaction is done.</p> <blockquote> <p>Because theoretical the DB can't be accessed by many users in the same time.</p> </blockquote> <p>Why not? DB in most cases is meant to be used concurrently. You have these DB isolation levels - READ_COMMITTED, READ_UNCOMMITTED, SERIALIZED etc. SERIALIZED is the case where your DB becomes single user access.</p>
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    1. USMariusz Jamro
    1. USBasanth Roy
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