Maps, primitives, File I/O:

java type system:

>> Java has two types of system:

• Alternatives such as int , boolean .. this type is accessed quickly

• Reference types such as Integer, Boolean. Its access is slower

>> The choice of type depends on the size of the application and available memory

• Each type of data holds a different size in memory:
• boolean – 1 bit
• byte – 8 bits
• short, char – 16 bits
• int, float – 32 bits

• long, double – 64 bits

• Boolean – 128 bits
• Byte – 128 bits
• Short, Character – 128 bits
• Integer, Float – 128 bits
• Long, Double – 192 bits

>> Alternatives variables are better to use but Java is not allowed to use them in the Genics and Reflection API

performance:

The performance of Java programs is highly dependent on the device it is running on and the compiler used

java exception:

An error occurs during program execution that disrupts its normal functioning

>> The error is transferred to the exception handler trying to find a way to complete the work and correct the error, if it does not find the program stops

>> One of the methods used to avoid program crashes and to detect and correct errors TRY - CATCH

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Scanning:

When we need input from the user or from file, as the simplest solution we use Scanning