• Java technology combing ArrayList


    Java technology combing – ArrayList combing ArrayList from source code and actual combat ArrayList premise 1、 Principle 2、 Parameters /** * Default initial capacity. */ private static final int DEFAULT_CAPACITY = 10; Default size /** * Shared empty array instance used for empty instances. */ private static final Object[] EMPTY_ELEMENTDATA = {}; /** * Shared […]

  • Configuring Oracle self boot on Linux 6


    Dbstart, dbshut modification (Oracle user) The premise is $oracle_ Home environment is set correctly, get $Oracle_ Home value, followed by sed -i ‘s/ORACLE_HOME_LISTNER=\$1/ORACLE_HOME_LISTNER=\$ORACLE_HOME/g’ $ORACLE_HOME/bin/dbstart sed -i ‘s/ORACLE_HOME_LISTNER=\$1/ORACLE_HOME_LISTNER=\$ORACLE_HOME/g’ $ORACLE_HOME/bin/dbshut #Verification grep -i “ORACLE_HOME_LISTNER=” $ORACLE_HOME/bin/dbstart grep -i “ORACLE_HOME_LISTNER=” $ORACLE_HOME/bin/dbshut /Etc / oratab modification (root user) sed -i ‘s/:N/:Y/g’ /etc/oratab #Verification tail /etc/oratab rc.local Boot file configuration (root) […]

  • Mac vscode debugging configuration


    Install go language debugging tool DLV premise Xcode command line tools need to be installed. Run the following command to install: xcode-select –install DLV installation go install github.com/derekparker/delve/cmd/dlv to configure to configure settings.json Goroot and gopath inClick vs code, click the code option in the top bar, select preferences, click settings, select extensions, click go […]

  • PLSQL call method


    CREATE OR REPLACE FUNCTION c_to_f (degree NUMBER) RETURN NUMBER IS buffer NUMBER; BEGIN buffer := (degree * 9/5) + 32; RETURN buffer; END; –The first prerequisite method must be created, not temporary select c_to_f(45) from dual; DECLARE a number; b number; c number; FUNCTION findMax(x IN number, y IN number) RETURN number IS z number; […]

  • The tar command under Linux is decompressed to the specified directory


    Unzip the tar command under Linux to the specified directory: #tar zxvf xx.tar.gz -C /xx//Put the xx.tar.gz Unzip it to / XX / if the directory / XX existsThis is a little different from the CP command. If the CP command does not exist, the directory will be created automatically!  

  • Error in installing mycli: could not find a version that satisfies


    Premise: PIP & PIP3 installed report errors: Could not find a version that satisfies the requirement mycli (from versions: ) No matching distribution found for mycli <p>Reason: network problems, sometimes unstable, use domestic image sources to speed up</p> Input: PIP install mycli – I http://pypi.douban.com/simple/ –trusted-host pypi.douban.com If the terminal appears as follows, it indicates […]

  • Java polymorphism


    It can be understood as a variety of forms of things. The manifestation of polymorphism: A reference to a parent class points to its own child class object. A reference to a parent class can also receive its own child class object.  The premise of polymorphism: It must be a relationship between classes, either inheritance […]

  • Unrecognized Mr import data to HBase tableoutputformat


    Environment: win10, compiler ideaPremise: all jar packages are imported automatically with mavenWhen writing Mr program, you need to import data to HBase, but the tableoutputformat class compiler cannot recognize it.You need to introduce the jar package into the pom.xml file. After checking, this class comes from the org.apache.hadoop.hbase.mapreduce packageIt depends on HBase server. The following […]

  • Regular password free backup of multiple MySQL databases and different hosts


    Set MySQL password free login configuration (if “MySQL client” is installed on the current host) Warning can be avoided: using a password on the command line interface can be inside [[email protected] ~]# mysql_config_editor set –login-path=confdb –user=xxxx –socket=/tmp/ dingding.log mysql.sock .X11-unix/ .font-unix/ sess_vutauod8dd2etpnugs0peb9845 .XIM-unix/ hsperfdata_root/ systemd-private-4fe3e89c1d0d4336b0f8eb906b922e7a-vgauthd.service-WuBPGJ/ zabbix_server_5297.pinger .ICE-unix/ systemd-private-4fe3e89c1d0d4336b0f8eb906b922e7a-vmtoolsd.service-6bsXLG/ zabbix_server_alerter.sock jetty- .Test-unix/ zabbix_server_preprocessing.sock [[email protected] ~]# mysql_config_editor […]