Hand design mode

The singleton pattern ensures that a class has only one instance and provides a global access point.

Java code

public class Test {
private static test = NULL;
Private Test () {
}
Public Static Test getinstance () {
if (test = = null) {
test = new test ();
} return
tes　T
}
}　　　　　　　

The above singleton pattern code, with deferred loading, generates instances when needed. However, multithreading can result in multiple instances.

Java code

Multithreading simultaneously accesses the following code. Generates multiple instances public
static Test getinstance () {
if (test = = null) {
test = new test　();　
}
return test;
}