System. setproperty ()

/*
* Set the system attributes of the specified key-pair Value
* Setproperty (string prop, string value );
*
* Number of shards:
* Prop-name of the system property.
* Value-value of the system attribute.
*
* Return value:
* If there is no previous value in the system attribute, null is returned.
*
* Throw:
* Securityexception-assume that the security manager exists and its checkpermission method does not agree to set the specified attribute.
* Nullpointerexception-assume that the key or value is null.
* Illegalargumentexception-assume that the key is null.
* Note: The system here refers to the JRE (runtime) system, not the OS.
*
*/

// Instance
System. setproperty ("property1", "ABC ");
System. setproperty ("property2", "def ");

// Set the first worker number as the global variable of the system! It can be obtained by system. getproperty ("variable"); in no matter where the project is located,

// System. setproperty is equivalent to a static variable, which exists in the memory!