0 Fundamentals of Android Development Java language Learning 02-Basic syntax

The first Java program

Here's a simple Java program that will print the string Hello World

Com.henancaiyun package, mainly used to solve the same name problem. Each class must be specified under a package.
Package Com.henancaiyun;

Import ClassA
Import Com.henancaiyun.ClassA;

Helloword class
public class Helloword {

Main static function
public static void Main (string[] args)
{
/* This is the first Java program
* It will print Hello World
* This is an example of a multiline comment
*/
String variable Helloword
String helloword= "Hello Word";
System output Hello Word character
System.out.println (Helloword);

}

}

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Com.henancaiyun package, mainly used to solve the same name problem. Each class must be specified under a package.
Package Com.henancaiyun;

Import Java.sql.Date;

Helloword class
public class Helloword {


Main static function
public static void Main (string[] args)
{
/* This is the first Java program
* It will print Hello World
* This is an example of a multiline comment
*/
String variable Helloword
String helloword= "Hello Word";

System output Hello Word character
System.out.println (Helloword);

Checkstudey ();

}

Data type
public static void Datatypestudey ()
{
BYTE h=10;
Short i=20;
int j=30;
Long k=30;
float l=0.000000000000000000000000000000000000000000001f;
Double m=0.0000000000000000000000000000000000000000000000000000000000000000000000000001;
Boolean flag=true;
Char c= ' 1 ';
String str= "I am Li bao Qing";
int [] intarray=new int []{1,2,3,4,5};
intarray[0]=0;
string [] strarray=new string []{"1", "2", "3"};
System.out.println (Intarray[0]);

 }
 //variable
 public static void Veriablestudey ()
 {
  int a=1;
 
  final int b=10;
  
  a=10;
  a=11;
  
  system.out.println (a);
  
 }
 
    //operator
  public static void Computechatstudy ()
  {
   /* arithmetic operator
   + Add-add operator on both sides of the value A + B equals $
   -subtraction-The left operand minus the right operand a–b equals -10
   * multiplication-the value on either side of the multiply operator is a * b equals a number
   /except Law-left operand divided by right operand b/a equals 2
   % modulo-left operand except right operand remainder b%a equals 0
   + + self increment-operand value increases 1 B + + equals 21
   ----the value of the operand is reduced by 1 B--equals
   */
   int a=1;
   int b=2;
   int c=a+b;
   c++;
   
   system.out.println (c);

/* Relational operators
* = Check if the values of the two operands are equal, the condition is true if they are equal. (A = = B) is False (not true).
! = Checks if the values of the two operands are equal, and the condition is true if the values are not equal. (A! = B) is true.
> Checks if the value of the left operand is greater than the value of the right operand, and if so the condition is true. (a> B) not true.
< checks if the value of the left operand is less than the value of the right operand, and if so the condition is true. (A <b) is true.
> = checks whether the value of the left operand is greater than or equal to the value of the right operand, and if so the condition is true. (a> = B) is false.
<= checks if the value of the left operand is less than or equal to the value of the right operand, and if so the condition is true. (a <= B) is true.
*/


Boolean flag= (A==B);

SYSTEM.OUT.PRINTLN (flag);

/* Logical operator
&& is called logic and operator. The condition is true when and only if two operands are true. (A && B) are false.
| | Called a logical OR operator. If any one of the two operands is true, the condition is true. (A | | B) is true.
！ is called a logical non-operator. The logical state used to reverse the operand. If the condition is true, the logical non-operator will get false.
*/
Boolean flag2= (A==b&&b==c);

SYSTEM.OUT.PRINTLN (flag);

/* Assignment operator
= Simple assignment operator, assigning the value of the right operand to the left operand C = A + B assigns the value obtained by A + B to c
+ = Plus and assignment operator, which adds the left operand and the right operand to the left operand C + = a equivalent to C = C + A
-= minus and assignment operator, which subtracts the left and right operands from the left operand c-= A is equivalent to C = c-a
* = Multiply and assign operators, which multiply the left and right operands by assigning A value to the left operand c * = a equivalent to C = c * A
/= In addition to and assignment operators, it assigns the left operand and the right operand to the left operand c/= A equivalent to C = c/a
* */
int h=0;
h+=2;//(h=h+2)
SYSTEM.OUT.PRINTLN (flag);
/* Conditional operator
* The conditional operator is also known as the ternary operator. The operator has 3 operands and needs to determine the value of a Boolean expression. The main decision of the operator is to decide which value should be assigned to the variable.
* */
int i= (h==0?1:0);
String name= (h==0? " LBQ ":" Lxq ");
SYSTEM.OUT.PRINTLN (flag);

}
Looping statements
public static void Circlestudey ()
{
While loop
int x = 10;
while (x < 20) {
System.out.print ("While loop of x:" + x);
x + +;
System.out.print ("\ n");
}

Do...while Cycle
x = 10;
do{
System.out.print ("Do...while cycle x:" + x);
x + +;
System.out.print ("\ n");
}while (x < 20);

For loop
for (int i = ten; i <; i = x+1) {

if (i==10)
Continue
if (i==12)
Break
System.out.print ("For Loop of x:" + i);
System.out.print ("\ n");
}

}

Judgment statement
public static void Checkstudey ()
{
int x = 10;
If statement
if (x < 20) {
System.out.print ("This is an if statement");
}
If...else statements
if (x < 20) {
System.out.print ("This is an if statement");
}else{
System.out.print ("This is the Else statement");
}
If...else if...else Statements
if (x = = 10) {
System.out.print ("Value of X is 10");
}else if (x = = 20) {
System.out.print ("Value of X is 20");
}else if (x = = 30) {
System.out.print ("Value of X is 30");
}else{
System.out.print ("This is Else statement");
}
Switch statement
Char grade = ' B ';

Switch (grade)
{
Case ' A ':
System.out.println ("excellent!");
Break
Case ' B ':
Case ' C ':
System.out.println ("Well-done");
Break
Case ' D ':
SYSTEM.OUT.PRINTLN ("You passed");
Case ' F ':
System.out.println ("Better try Again");
Break
Default:
System.out.println ("Invalid grade");
}
System.out.println ("Your grade is" + grade);

  }
    
    //Method Learning
     public static void Method ()
     {
      int a=1;
      int b=2;
      int Maxvalue=max (A, b);
      
      system.out.println (maxValue);
    
    
    /** Returns a larger value for two integer variable data */
      public static int max (int num1, int num2) {
        int result;
        if (Num1 > Num2)
           result = NUM1;
        Else
           result = num2;

return result;
}

/*
public static void Classstudey ()
{
A dog.
Dog Hashishiqi=new Dog ();
Hashishiqi.breed= "Hashiqi";
hashishiqi.age=1;
Hashishiqi.color= "Gray";
Another dog.
Dog Muyangquan=new Dog ();
Muyangquan.breed= "Hashiqi";
muyangquan.age=1;
Muyangquan.color= "Gray";

}
*/

}

0 Fundamentals of Android Development Java language Learning 02-Basic syntax