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Common methods of Java StringBuffer StringBuffer is a variable length string Example 1: Additional deletion insert reversal append addition Delete delete Insert insert reverse reversal package character; public class TestString { public static void main(String[] args) { String str1 = "let there "; StringBuffer sb = n ...

Concurrent queue: In concurrent queues, JDK has two implementations: Concurrent LinkedQueue: Non-blocking Queue BlockingQueue: Blocking Queue   Differences between blocking and non-blocking queues: When a blocking queue is included in a queue operation, if it exceeds the total number of queues, it will wait at this time; when a queue is e ...

HashSet ensures that elements are not duplicated? To be more direct, in fact, the add() method of HashSet calls the put() method of HashMap. We all know that key of Map does not allow duplication, which is actually the true principle that HashSet can ensure that elements are not duplicated. Take a loo ...

Because the ByteBuffer provided in JDK can not be dynamically expanded and the API is complex to use, Netty provides ByteBuffer. The API of Bytebuf is more convenient and can be expanded dynamically. It provides a variety of implementations of Bytebuf and an efficient zero-copy mechanism. Operation of ByteBuf ByteBuf has three important attribu ...

Basic encoding is a standard BASE64 encoding, which is used to handle conventional requirements: the output content does not add line breaks, and the output is composed of letters plus numbers. Recently, I made a Web template, in which I want to use Base64 background image. Although there are ready- ...

Make tomcat image: JDK and tomcat images are constructed based on centos 7.2.1511 basic images provided by the government. First, JDK images are constructed, and then tomcat images are constructed based on JDK images. Building JDK Mirror Download the Basic Mirror Centos: docker pull centos Execu ...

HashMap features The bottom layer of HashMap is array + linked list + red-black tree (JDK 1.8) HashMap is stored in key-value form, where key can be allowed to be null but can only be one, and key does not allow duplication. HashMap is thread insecure. The order in which HashMap is stored and traversed may be inconsistent. When HashMap saves d ...

Label (Space Separation): Uncategorized The package where the log function code resides org.apache.ibatis.logging Loading order of log module mybatis does not have its own log module. It uses third-party logs (and jdk has its own logs) Log loading order slf4J_commonsLoging_Log4J2_Log4J_JdkLog Related code Declare the loading order in the stati ...

Stand-alone version configuration Upload installation package Upload to / bigdata decompression Unzip to / apps directory tar -zxvf /bigdata/hadoop-2.7.1.tar.gz -C /apps Configuring environment variables vi /etc/profile #In the final increase export HADOOP_HOME=/apps/hadoop-2.7.1 export PAT ...

1. What is the agency model? Agent pattern is one of the most common design patterns. When the target class is inconvenient to operate, another class is used instead of the target class to perform the same operation. Intention: Provide a proxy for other objects to control access to this object. II. Static Agent and Dynamic Agent Static proxy ...