Java Basics-Learning notes (ii)

1. Common Java Data types

Data type	Key words	Number of bytes occupied
Boolean type	Boolean	1
BYTE type	Byte	1
Character type	Char	1
Short-integer	Short	2
Integral type	Int	4
Long integer type	Long	8
Floating point Type	Float	4
Double-precision Type	Double	8

2, the conversion between ordinary data types, an example to illustrate the situation

1  Public Static voidMain (String args[])2     {3         intX=1;4         floatf=2.0f;//if no f is added, the default is double type5         DoubleE=f;//implicit type conversion assignment variable byte < assigned variable byte6         byteB= (byte) x;//coercion type conversion assignment variable byte > assigned variable byte7         CharC= ' A ' +1; 8         //b=b-1; Error shaping defaults to int type9e=x+f+b;TenSystem.out.println (e);//Output 4.0 Output result Select the type of the highest byte in an expression OneSystem.out.println (c);//Output B A}

3. Java Rules for identifiers

• Consists of letters, numbers, underscores (_), Dollar signs ($);
• Identifiers cannot begin with a number.

4. Overloading of functions

It is possible to have more than one function of the same name in the same class, as long as the number of arguments or the data type is different, as shown in the following example:

1  Public Static voidMain (String args[])2     {3Add (3,4);4Add (3,4,5);5Add (1.0,2.0,3.0);6     }7      Public Static intAddintXinty)8     {9System.out.println (x+y);Ten         returnx+y; One     } A      Public Static intAddintXintYintz) -     { -System.out.println (x+y+z); the         returnx+y+Z; -     } -      Public Static DoubleAddDoubleXDoubleYDoublez) -     { +System.out.println (x+y+z); -         returnX+y+z;

5. Arithmetic operators (small places to note)

1  Public Static voidMain (String args[])2     {3         intx=5,y,z=312;4         floatF;5Y=x%-2;6System.out.println (y);//Output 1, indicating that the residual result is not affected by the negative sign7y=z/300*300; 8System.out.println (y);//output 300 Instead of 312, because Z is an integer, divided by 300, the result is 1.9F=x/2;TenSystem.out.println (f);//output 2.0, because F is a floating-point type One         intA=1,c=1, b,d; Ab=a++;//after the first operation , the self-increment -System.out.println ("a=" +a+ ", b=" +b)//Output A=2,b=1 -D=++c;//first self-increment after operation theSystem.out.println ("c=" +c+ ", d=" +d);//Output c=2,d=2 -}

Java Basics-Learning notes (ii)