Data type conversion

1. Automatic type conversion ： A small range of data is stored in a large range of variables

2. Cast ： Cast ： A large range of data is stored in a small range of variables .

Be careful ： It may be stored . It is also possible that a large range of data exceeds the range of a small range of data , At this time, the accuracy of the data will be lost

ublic static void main(String[] args) {

		// Automatic type conversion ： A small range of data is stored in a large range of variables 
		byte num1 = 100;
		int num2 =num1;
		System.out.println(num2);//100
		
		// Cast ： A large range of data is stored in a small range of variables . Be careful ： It may be stored . It is also possible that a large range of data exceeds the range of a small range of data , At this time, the accuracy of the data will be lost 
		int num3 =129;
		byte num4 =(byte)num3;
		System.out.println(num4);//120
	}
	

If there is a strong conversion between decimal and integer, precision may be lost

package cn.bdqn.Teacherdemo1;

public class Demo3 {

	public static void main(String[] args) {
		int before = 20; // apple Notebook market share 
		double rise = 9.8; //  Increased share 
		int now = (int)(before + rise); //  Current share 
		System.out.println(" Current share ："+now);//29   Loss of data accuracy 
	}

}

3.  According to the function of the operator , We divide operators into the following categories

Arithmetic operator 、 Assignment operator 、 Relational operator 、 Logical operators 、 An operator And other operators

1. Arithmetic operator

For all kinds of numerical operations . Including plus (+)、 reduce (-)、 ride (*)、 except (/)、 Seeking remainder ( Or modular operation ,%)、 Self increasing (++)、 Self reduction (--) There are seven kinds of . Compound arithmetic operators ：+= -= *= /= %=

2. Relational operator

Used in comparison operations . Include greater than (>)、 Less than (=)、 Less than or equal to (<=) And are not equal to (!=) Six kinds .

The operation result of relational operator is Boolean . Either for true, Either for false. 
= For the assignment operator ,== Is equal to operator
>、<、>=、<= The operator takes precedence over ==、!=
 >、<、>=、<= Operator only supports data comparison of numeric type

3. Logical operators

For logical operations . Include and (&&)、 or (||)、 Not (!) Three .

4. Bit operation Operator

The amount of work involved , To operate in bits . Including bit and (&)、 Bit or (|)、 Bit non (~)、 Bit exclusive or (^)、 Move left (<>) Six kinds .

5. Assignment operator

For assignment operations , It is divided into simple assignment (=)、 Compound arithmetic assignment (+=,-=,*=,/=,%=) And compound bit operations

(&=,|=,^=,>>=,<<=) There are eleven kinds of three kinds .

4. Here we can distinguish ++  Self increasing   -- The use of self subtraction

++ or -- The difference between before and after variables
  For a single variable ,++ perhaps -- Whether before or after the variable , Variables will increase automatically 1 Or self reducing 1
For the variables involved in the operation ,++ or -- After the variable , Variables are involved in the operation first , After participating in the calculation , Then carry out self increase or self decrease
For the variables involved in the operation ,++ or -- Before the variable , Variables increase or decrease first , After self increase or self decrease , And then I'll take part in the calculation

public class Demo7 {

	public static void main(String[] args) {
		int num1 = 10;
		int num2 = num1++;
		System.out.println("num1=" + num1);// num1=11
		System.out.println("num2=" + num2);// num2 = 10

		int num3 = 10;
		int num4 = ++num3;
		System.out.println("num3="+num3);//num3 = 11
		System.out.println("num4="+num4);//num4 = 11
		

	}

}

5. Data exchange can be realized by assignment operator

Conditions required ： Third party temporary storage  

=
// Operator operator
public class Operator {

	public static void main(String[] args) {

		/*
		 *  Data exchange with the help of assignment operators 
		 *  Need to bring three temporary storage 
		 */
		int n=5;
		int t =6;
		int in;
		in = n;
		n =t;
		t = in;
		System.out.println(n+"   "+t);//n=6,t=5
		
	}
	

}