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Data Types in Java Learning data types is an elementary step in knowledge of java. Consider You want to do an operation as 2+2 = 4 , then what all we need. We need something to keep 2 in. Learning java is not know how of how to add , but how Java will add.  This is easier to understand that 2+2  will not be a long thing , but consider adding 23493094034900390349003 + 1 , most compilers will either take a long time, or crash , or simply throw an exception. Learn how to add such numbers in Java, is study of such stuff. I will try to provide intersting examples to understand this . For the beginners , Java has 8 primitive types , these data types provide the basic necessity . These 8 primitive types are : byte - The range of values from -127 to 128 . I would rather use byte where i want to save memory. byte is used as index values , and place where the data types and storage is important. short - The value ranges from -32768 to 32768. The value i have entered earlier can not be added using this data type. int - The value ranges for int data type in Java is -2,147,483,648 to 2,147,483,647 .The int values can be unsigned and signed. By default int is signed. char - Enough with numbers, the char is used to store characters in Java. Java is a strongly typed language , and developers coming from C/C++ platform must not confuse char with string.  String is not a primitive data type in Java. I am not saying String is not a data type , it is just not primitive data type. The minimum value of char is '\u0000' and the maximum value is '\uffff' ( can be read as (0,32768)  float - Often used to represent the decimals valurs , float is not recommended for use in production in general. Prefer using long instead long - initalised with L in the last , long is used to represent the decimal numbers,9,223,372,036,854,775,808 and a maximum value of 9,223,372,036,854,775,807. So this is my choice to add very large numbers double - If you have the decimal values , those are not very large , and needs to be accessed frequently , double is the choice boolean - the data type to choose when the decision is in true or false. boolean is used to store the data type as a boolean value. Learning the use of boolean values will help a long way in going to write complex logic. Default value of boolean is false.    Example of how to use Java integer type is given here Uninitalized local variables in Java will cause a compiler error. Even though Java will initialize the static variables , it is still recommended to initialize the variables. One advantage of Java is that variables can be initialised where they are needed , unlike C , where the initialization had to take place at the top. Here is an example what will happen in case the uninitialized Java Data type is complied and run.