JAVA while, for, if, switch, loop control

While Loop statement:

while (Boolean expression)//Boolean expression value is true on execution loop, otherwise false jumps out of loop　　

{statement }

 //while cycle, calculate 1 to 100
PackageXunhuan; Public classXun { Public Static voidMain (string[] args) {intSum=0,i,a=1,s=0;  for(i=0;i<=100;i++) Sum=sum+i;  while(a<101) {s=s+A; A++;        } System.out.println (s);    SYSTEM.OUT.PRINTLN (sum); }}

Do......while Loop statement:

　　 Do {

Statement}while (Boolean expression)

　The following: Registration procedure

1  PackageXunhuan;2 3 ImportJava.util.Scanner;4 5  Public classDemo {6      Public Static voidMain (string[] args) {7Scanner sc=NewScanner (system.in); Create a scanner and wait for console input8String zf1= "1"; Create two strings, save two input values9String zf2= "2";Ten          Do{ OneSystem.out.println ("Please enter password"); AZF1 =Sc.nextline (); Enter your password for the first time -System.out.println ("Please enter password"); -ZF2 =Sc.nextline (); Enter the password for the second time the             if(!zf1.equals (ZF2))//Determine if the password is equal to two times -SYSTEM.OUT.PRINTLN ("Password is inconsistent, please re-enter"); -} while(!zf1.equals (ZF2)); The Do...while loop is not exited until the password is incorrect -SYSTEM.OUT.PRINTLN ("Registered successfully! "); +     } -}

For Loop statement (themost commonly used expression in Java )

For (initialization expression 1; Boolean expression 2; expression 3)　　 {//initialization expression 1: Run once before the start of the loop, can be used as an assignment, run only once;

Statement//Boolean expression 2: Returns a Boolean value, whether the control program continues execution;

} //Expression 3: Typically an assignment expression that resumes execution after a loop is completed;

 PackageXunhuan;/*** Hundred money buy hundred chicken problem *@authorNGB **/ Public classBaiji { Public Static voidMain (string[] args) {inti,j,k;  for(i=1;i<=20;i++){         for(j=1;j<=33;j++){             for(k=3;k<=99;k+=3){                if(i*5+j*3+k/3==100)//Hundred dollars                    if(i+j+k==100) {//Hundred ChickensSYSTEM.OUT.PRINTLN ("Rooster has" +i+ "only" + "hen has" +j+ "only" + "chicks have" +k+ "only"); }            }        }    }}}

1  PackageXunhuan;2 /**3 * Use for loop to calculate 1 plus to4  * @authorNGB5  *6  */7  Public classForxunhuang {8      Public Static voidMain (string[] args) {9         intSum=0;Ten         inti; One          for(i=0;i<101;i++){ Asum=sum+i;} -SYSTEM.OUT.PRINTLN ("The result is:" +sum); -     } the}

foreach statement

Grammar:

for (type X:obj) {statement

}//type x: The loop variable, which in turn assigns the value of obj to x obj: A collection that can be traversed, such as an array

　　

 PackageXunhuan;/*** foreach loop, traversing array *@authorNGB **/ Public classForeach_xunhuang { Public Static voidMain (string[] args) {intarr[]={1,2,3,4,5,6};  for(intB:arr) {            intI=0; System.out.println ("Arr[i]=" +b); I++; }    }}

If condition statement

if (Boolean expression) {statement};

if (Boolean expression) {statement} else{statement};

if (Boolean expression) {statement} elseif (Boolean expression) {statement}....else{statement};

Switch Multi-branch statement

 PackageXunhuan;ImportJava.util.Scanner; Public classSwitch_yuju { Public Static voidMain (string[] args) {Scanner sc=NewScanner (system.in); intA; System.out.println ("Please enter a score"); A=Sc.nextint (); Switch(a) { Case10:     Case9:system.out.println ("score is excellent"); Break;  Case8:     Case7:system.out.println ("score is good"); Break;  Case6:system.out.println ("score is passed"); Break;  Case5:     Case4:     Case3:     Case2:     Case1:     Case0:SYSTEM.OUT.PRINTLN ("result is poor"); Break; default: System.out.println ("The result you entered is invalid"); }}}

JAVA while, for, if, switch, loop control