The diamond problem in Java is a problem related to multiple inheritance. It occurs when a class inherits from two or more classes that share a common ancestor. In Java, inheritance is a relation between two classes, the parent and child class. The child class (sub-class) inherits all the properties of the parent class (super-class) . There are different types of inheritance such as single, multiple, multi-level, and hybrid inheritance. However, Java does not support multiple inheritance because of the diamond problem.

The diamond problem arises when a child class inherits properties from more than one parent class and the methods for the parents are the same (method name and parameters are exactly the same), then the child gets confused about which method will be called. This problem in Java is called the diamond problem. For example, if class D is trying to inherit from class B and class C, that is not allowed in Java. It is an ambiguity that can arise as a consequence of allowing multiple inheritance.

Java solves the diamond problem by using default methods and interfaces. With the help of these two concepts, multiple inheritances are possible. The abstract method and the default method are comparable. The only difference is that it is defined inside the interfaces with the default implementation. You dont need to override these procedures since they have already begun to use these interfaces.

In summary, the diamond problem is a problem related to multiple inheritance in Java. It occurs when a class inherits from two or more classes that share a common ancestor. Java solves this problem by using default methods and interfaces.