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In development,we can use the Util which already exists.
For example:
org.apache.commons.lang.StringUtils;
System.arraycopy();
package org.apache.commons.beanutils
org.apache.ftpserver.util.EncryptUtils

 

package org.apache.commons.lang
这个包下有很多有用的工具类可以直接用
StringUtils
WordUtils
ObjectUtils
NumberUtils
ClassUtils
ArrayUtils

 

UML:
The Activity Diagram
Sequence Diagram

thread:
三个不同级别的线程同步程度
synchronzed
volatile value is only can be read,can't not write.
atom is extended from volation.
锁定时间越短越好，锁定范围越小越好

relativity [,relə'tivəti]
n. 相对论；相关性；相对性