what is the "" and "" in JAVA?

3.8 Special Initialization Methods

At the level of the Java Virtual Machine, every constructor appears as an instance initialization method that has the special name <init>. This name is supplied by a Java compiler. Because the name <init> is not a valid identifier, it cannot be used directly by a Java programmer. Instance initialization methods may only be invoked within the Java Virtual Machine by the invokespecial instruction, and they may only be invoked on uninitialized class instances. An instance initialization method takes on the access permissions of the constructor from which it was derived.

At the level of the Java Virtual Machine, a class or interface is initialized by invoking its class or interface initialization methodwith no arguments. The initialization method of a class or interface has the special name <clinit>. This name is supplied by a Java compiler. Because the name <clinit> is not a valid identifier, it cannot be used directly by a Java programmer. Class and interface initialization methods are invoked implicitly by the Java Virtual Machine; they are never invoked directly from Java code or directly from any Java Virtual Machine instruction, but are only invoked indirectly as part of the class initialization process