Data types in Java are divided into two important groups according to how variables of this type are related and the values stored in them.
What will the following code output?
var a = 10;
var b = a;
a = 20;
System.out.print(b);
10 will be output, because with the assignment b = a, the number 10, which at this moment is contained in a, will be written into the variable b.
If you write
var a = "string";
var b = a;
Primitive data types in Java:
7
,-198
, 0
and so onThere are different ways to present data in programs.
There are strings - character sets in quotes like "Hello, World!"
. There are integers - for example, 7
, -198
, 0
. These are two different categories of information - two different data types.
The multiplication operation makes sense for integers but it does not make sense for strings: to multiply the word "mother" by the word "notepad" is nonsense.
The data type determines what can be done with the elements of a specific set of information.
A programming language recognizes types. Therefore, Java will not allow us to multiply a line by line (“multiply text by text”). But it will allow to multiply an integer by another integer. The presence of types and such restrictions in the language protects programs from random errors.
Unlike strings, numbers do not need to be wrapped in quotes. To print the number 5, just write:
System.out.print(5);
Note that the number 5
and the string "5"
are completely different things, although the output of println
for this data is identical.
Integers (1
, 34
, -19
, etc.) and rational numbers (1.3
, 1.0
, -14.324
, etc.) are two separate types data. This separation is associated with the characteristics of the device computers. There are other types, we will get to know them later.
Here is another example, but with a rational number:
System.out.print(10.234);
The lines in programming are called "strings", and the lines of text files are called "lines". For example, the code above has one line (lines), and there are no lines (strings). In all the lessons we will say string to indicate the data type "string", and line to indicate lines (lines) in files).
Programmers themselves can create new data types, albeit with certain restrictions.
Display the number -0.304
.
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Tests are designed so that they test the solution in different ways and against different data. Often the solution works with one kind of input data but doesn't work with others. Check the «Tests» tab to figure this out, you can find hints at the error output.
It's fine. 🙆 One task in programming can be solved in many different ways. If your code passed all tests, it complies with the task conditions.
In some rare cases, the solution may be adjusted to the tests, but this can be seen immediately.
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