Getting Started with Java-selection and looping statements

• If...else ... Statement

• 1  Public classIfdemo {2 3     /**4      * @paramargs5      */6      Public Static voidMain (string[] args) {7         //TODO auto-generated Method Stub8         intX=20;9         intY=12;TenSYSTEM.OUT.PRINTLN ("****** compare start ******"); One         if(x<y) { ASystem.out.println ("x is smaller than Y!") "); -}Else if(x>y) { -System.out.println ("x is bigger than Y!") "); the}Else{ -System.out.println ("x and y are equal! "); -         } -SYSTEM.OUT.PRINTLN ("****** comparison complete ******"); +}

  The results are as follows:

• Compare start ******x greater than Y! ****** comparison completed ******

• Swich statements
• 　

  1  Public classSwitchdemo {2 3     /**4      * @paramargs5      */6      Public Static voidMain (string[] args) {7         //TODO auto-generated Method Stub8         intX=3;9         intY=6;Ten         CharOper= ' + '; One         Switch(oper) { A          Case+:{ -System.out.println ("x+y=" + (x+y)); -              Break;//Exit Switch the         } -          Case‘-‘:{ -System.out.println ("x-y=" + (X-y)); -              Break; +         } -          Case‘*‘:{ +System.out.println ("x*y=" + (x*y)); A              Break; at         } -          Case‘/‘:{ -System.out.println ("x/y=" + (x/y)); -              Break; -         } -         default:{ inSystem.out.println ("Unknown operation! "); -              Break; to         } +         } -     } the  *}

  If the break statement is not set, the program does not jump out of the switch

• While

• 1  Public classWhiledemo {2 3     /**4      * @paramargs5      */6      Public Static voidMain (string[] args) {7         //TODO auto-generated Method Stub8         intX=1;9         intSum=0;Ten          while(x<=10){ Onesum+=x; AX + +; -         } -SYSTEM.OUT.PRINTLN ("Cumulative sum of 1 to 10 for:" +sum); the     } -  -}

  While is a looping statement and a conditional judgment statement. When the implementation does not know how many times the loop executes, it uses the while loop.

• Do...while

• 1  Public classDowhiledemo {2 3     /**4      * @paramargs5      */6      Public Static voidMain (string[] args) {7         //TODO auto-generated Method Stub8         intX=1;9         intSum=0;Ten          Do{ Onesum+=x; AX + +; -} while(x<=10); -System.out.println ("1 to 10 and for:" +sum); the     } -  -}

  Do...while ... The operation of the loop and the while loop is the same, but it is executed at least once.

• For

• 1  Public classFordemo {2 3     /**4      * @paramargs5      */6      Public Static voidMain (string[] args) {7         //TODO auto-generated Method Stub8         intSum=0;9          for(intx=1;x<=10;x++){Tensum+=x; One         } ASystem.out.println ("1 to 10 of the and for:"); -     } -  the}

  (initial value of assignment; Judgment condition; assignment increment or decrement)

• Nesting of loops

• 1  Public classFornesteddemo {2 3     /**4      * @paramargs5      */6      Public Static voidMain (string[] args) {7         //TODO auto-generated Method Stub8          for(inti=1;i<=9;i++){9              for(intj=1;j<=i;j++){TenSystem.out.print (i+ "*" +j+ "=" + (i*j) + "\ T"); One             } ASystem.out.print ("\ n"); -         } -     } the  -}

  The results are as follows:

• 1*1=1    2*1=2    2*2=4    3*1=3    3*2=6    3*3=9    4*1=4    4*2=8    4*3=12    4*4=16    5 *1=5    5*2=10    5*3=15    5*4=20    5*5=25    6*1=6    6*2=12    6*3=18    6*4=24    6*5=    6*6=36    7*1=7    7*2=14    7*3=21    7*4=28    7*5=35 7*6=42 7*7=49    8*1=8    8*2=16    8*3=24    8*4=32    8*5=40    8*6=48    8*7=56    8*8=64    9*1=9    9*2=18    9*3=27    9*4=36    9*5=45    9*6=54    9*7=63    9*8=72    9*9=81    

• Interruption of the Loop
  • • The break statement can force the program to interrupt the loop, and the program will leave the loop when execution breaks.
    • The continue statement can force the program to jump to the beginning of the loop;

Getting Started with Java-selection and looping statements