How does System.out.printIn () accept integers?

Question

So, I started learning java a few days ago and got a question. For the following expression:

String foo=123; 

is not allowed. However, in System.out.printIn() we can use something like:

 int x=5; System.out.println(x); 

Since implicit assignment of an integer to a string is not allowed, why does the expression above work? Can anyone give a detailed explanation? I also wonder when we can use this implicit thing, and when we cannot.

Answer 1

There are so many overloaded PrintStream System.out methods:

 println(boolean x) println(char x) println(int x) println(long x) println(float x) println(double x) println(char x[]) println(String x) println(Object x) 

Answer 2

The reason you can call println with an integer is because the method is overloaded. Basically, there are several methods called println, and one of them takes an integer.

Take a look here: PrintStream

Answer 3

The static out member of the System class is PrintStream , which has a method with signature println(int) .

Answer 4

Check out the API on PrintStream ( System.out - PrintStream ). It has methods println() , println(boolean) , println(char) , println(char[] ), println(double) , println(float) , println(int) , println(long) , println(Object) and println(String) . This is called method overloading (scroll down to find the section on method overloading).

If you want to create a String from an integer literal, you can put quotation marks there ( String s = "123"; ) or use Integer.toString ( String s = Integer.toString(123); ) or String.valueOf ( String s = String.valueOf(123); ).

Answer 5

Im assuming you don't have println not printin, java has a println function for each data type, so you can call println on booleans, ints, strings, ect and choose the right function. Of course, you cannot assign an integer to a string variable, because these are different types.