The key to learning Java without taking detours is: 1. Understand core concepts and grammar; 2. Practice more; 3. Understand memory management and garbage collection; 4. Join online communities; 5. Read other people’s code; 6. Understand common libraries and frameworks; 7. Learn to deal with common mistakes; 8. Make a learning plan and proceed step by step. These methods can help you master Java programming efficiently.

Learning Java requires learning basic syntax, object-oriented programming, collection frameworks, exception handling, multithreading, I/O streaming, JDBC, network programming, and advanced features such as reflection and annotation. 1. The basic syntax includes variables, data types, operators and control flow statements. 2. Object-oriented programming covers classes, objects, inheritance, polymorphism, encapsulation and abstraction. 3. The collection framework involves ArrayList, LinkedList, HashSet, and HashMap. 4. Exception handling ensures program robustness through try-catch block. 5. Multithreaded programming requires understanding of thread life cycle and synchronization. 6. I/O streams are used for data reading, writing and file operations. 7. JDBC is used to interact with databases. 8. Network programming passes S

To connect Oracle database to Tableau for data visualization, you need to follow the following steps: 1. Configure Oracle database connection in Tableau, use ODBC or JDBC drivers; 2. Explore data and create visualizations, such as bar charts, etc.; 3. Optimize SQL queries and indexes to improve performance; 4. Use Oracle's complex data types and functions to implement through custom SQL queries; 5. Create materialized views to improve query speed; 6. Use Tableau's interactive functions such as dashboard for in-depth analysis.

In Oracle database, the steps to configure parallel query to improve performance include: 1. Set at the database level, and implement it by modifying initialization parameters such as PARALLEL_DEGREE_POLICY and PARALLEL_MAX_SERVERS; 2. Set at the session level, adjust the parallelism of the current session through the ALTERSESSION command; 3. Consider key points such as parallelism, resource management and data distribution; 4. Improve performance by optimizing query planning, adjusting parallelism and monitoring and tuning. These steps help to take full advantage of parallel queries and significantly improve the query performance of the database.

The steps to connect to an Oracle database connection pool using JDBC include: 1) Configure the connection pool, 2) Get the connection from the connection pool, 3) Perform SQL operations, and 4) Close the resources. Use OracleUCP to effectively manage connections and improve performance.

Guide to Installation, Switching and Management of Java Versions in CentOS Systems In the CentOS environment, especially when multiple projects coexist, it is crucial to efficiently manage different Java versions. This article will explain in detail the installation, switching and management methods of Java versions in CentOS system. Java version installation uses yum to install system update: first update the system package: sudoyumupdate-y install the specified JDK version: For example, install OpenJDK8 and OpenJDK11: sudoyuminstalljava-1.8.0-openjdk-devel-ysudoyumi

The starting point of writing SQL code is to clarify the requirements. 1) Understand the problem you want to solve and determine the relationship between the required data and tables. 2) Start designing queries from simple SELECT statements and gradually increase complexity. 3) Use visualization tools to understand table structure and consider using JOIN when queries are complex. 4) Test the query and use the EXPLAIN command to optimize performance to avoid common pitfalls such as NULL value processing and inappropriate index use.

In Oracle database, if you want to not return the value of a certain field when querying, you can use the following three methods: Only list the required fields in the SELECT statement and do not select the unwanted fields. Create views to simplify queries, but pay attention to the complexity and maintenance costs of the views. Excluding unwanted columns using subqueries or JOINs is suitable for dynamic exclusion of columns, but may affect query performance. Each method has its applicable scenarios and potential disadvantages, and the most suitable method needs to be selected based on specific needs and performance considerations.