Java loop variable

Method: A fragment that completes a specific function code.

Format: [modifier 1 modifier 2 ...] Return value type method name (formal parameter list) {

Java statement;

}

Formal parameters: Used to receive data from outside input when the method is invoked.

Argument: The data that is actually passed to the method when the method is called.

Return value: Returns to the environment data that called it after the method has finished executing

Return value type: Pre-agreed return value data type, if no return value, you must give void

The calling method is used in the Java language: Object name. Method Name (argument list).

Number of arguments, data type and order must match the invocation of the method declaration form parameter list

The return statement terminates the run of the method and specifies the type to return

Only values are passed in Java

Simple reading of the keyboard input string:

Scanner input =new Scanner (systrm.in);

String str =input.nextline ();

String str =input.next ();

int Str=input.nextint ();

System.out.println (str);

Sequential structure:

Java's basic structure is the sequential structure, unless otherwise specified, in order to execute a sequential structure of a simple algorithm, between statements and statements, between boxes and boxes in order from top to bottom, it is a number of sequentially executed processing steps.

If single structure:

Double I=6*math.random ();//math.random () produces a random number of 0~1

Double J=6*math.random ();//6*math.random () generation [0,5]

Double K=6*math.random ();

IoT count= (int) (I+J+J);

if (count>15) {

System.out.printlan ("Good luck");

}

if (count>=10&&count<=15) {

System.out.printlan ("Luck Class");

}

System.out.println ("Got" +count+ "points");

If else double-select structure: If the condition is true to perform an action, false to perform another operation

If the conditional expression is true, the statement block 1 is executed, otherwise the statement block 2 is executed.

Double R =4*math.random ();//Generate random number [0,4]

Double Are=math.pi*math.pow (r,2); the PI value defined in//math Math.pow (R.2) is the square of R

Double Cir =2*math.pi*r;

System.out.println ("Radius:" +r);

System.out.println ("area:" +are);

System.out.println ("Perimeter is:" +cir);

if (ARE>=CIR) {

System.out.println ("area greater than perimeter");

}else{

SYSTEM.OUT.PRINTLN ("circumference greater than area");

}

If else if else multi-select structure

if (Boolean expression 1) {

Statement Block 1;

}else if (Boolean expression 2) {

Statement Block 2;

}else if (boolean expression N) {

statement block N;

}else{

Statement block N+1;

}

public class IfTest3 {
public static void Main (string[] args) {
int age = (int) (Math.random ());
System.out.print ("Age is" + Ages + ", belongs to");

if (age < 15) {
System.out.println ("Children,");
} else if (age < 25) {
SYSTEM.OUT.PRINTLN ("Youth,");
} else if (age < 45) {
System.out.println ("Middle-aged,");
} else if (age < 65) {
System.out.println ("Middle-aged,");
} else if (age < 85) {
System.out.println ("old Age,");
} else {
System.out.println ("Loushing,");
}
}
}

Switch multi-select structure: Perform different actions depending on the expression

Switch statement: The case label must be an integer or an enumeration and cannot be a string.

switch (expression) {//byte,int,char,short and enum-type.

Case value 1;//value 1 must be constant

Statement sequence;

break;//Each statement ends with a break

Case value 2;

Statement sequence;

Break

...

default;//dispensable

Default statement;

}

The switch statement executes at the case label that matches the value of the expression and executes until the break statement or at the end of the switch statement. Does not match the case value, the next statement is entered.

public class vir{

public static void Main (String[]args) {

char c = ' a ';

int rand= (int) (26*math.random ());//(int) cast to int type produces a random number of [0,25]

Char c2= (char) (C+rand);

System.out.print (c2+ ";");

Switch (C2) {

Case= ' a '://Use case through, output all characters until break is encountered

Case= ' E ':

Case= ' I ':

Case= ' O ':

case= ' u ':

System.out.println ("vowel");

Break

Case= ' y ':

Case= ' W ':

System.out.println ("Semivowels");

Break

Default

System.out.println ("consonant");

}

}

Example:

System.out.print ("Please enter the month:");
int month = (int) (1+math.random () *12);
if (month>0&&month<13) {
Switch (month) {
Case 2:
System.out.println ("28 Days");
Break
Case 4:
Case 6:
Case 9:
Case 11:
System.out.println ("30 days");
Break
Default
System.out.println ("31 days");
}

}else{
System.out.println ("The month you entered is not legal! ");
}

While loop structure;

While statement format:

while (Boolean expression) {

Circulation body;

}

1. When the loop starts, the value of the Boolean expression is evaluated once, and if the condition is true, the loop body is executed. And for each subsequent cycle. will be recalculated once.

2. The statement should loop toward the end of the statement, otherwise die loop.

public class test{

public static void Main (string[] args) {

int i=0;

int sum=0;

while (i<100) {//Loop condition

sum+=i;//Calculate sum

i++;

}

System.out.println ("sum=" +sum);

}

}

Do and loop

bo=

Circulation body;

}while (boolean expression);

Execute the judgment first, at least once.

public class test{

public static void Main (string[] args) {

int i=0;

int sum=0;

do{

Sum+=i;

i++;

}while (i<=100);

System.out.println ("sum=" +sum);

}

}

The difference between while and dowhile

Dowhile is executed at least once.

int a = 0;

while (a<0) {

System.out.println (a);

i++;

}

SYSTEM.OUT.PRINTLN ("******");

a=0;

do{

System.out.println (a);

i++;

}while (a<0);

For loop

1.for Loop statement supports a common structure for iterations

Format:

for (initial expression; boolean-expression; stepping) {

Circulation body;

}

The For loop is initialized before the first iteration, then the conditional test is performed, and it is stepped at each iteration;

1. Initialize the initial value of the loop variable

2. Conditional expressions are judged as Boolean types

3. The iterative factor controls the increment or decrement of the cyclic variable

For (an initial expression; a Boolean expression; an iteration factor) {
Circulation body;
}

public class Fortest {
public static void Main (String args[]) {
int sum = 0;
for (int i = 0; I <=; i++) {
sum + = i;
}
System.out.println ("sum=" + Sum);

for (int i=9;i>0;i--) {
System.out.println (i);
}

for (int i=90;i>0;i-=3) {
System.out.println (i);
}
}
}

Java loop variable