17. Java Process Control

First, IF

1. The first form: if

if (logical expression) {    statement 1;    Statement 2;    ...}

You can omit {} when there is only one statement in the IF

2, the second type: If-else

if (logical expression) {        else  {        statement block 2;}

3, the Third kind of novice: If-else If-else

if (logical expression)        {elseif(logical expression) {        else  {        statement block 3; }

Second, switch statement

Switch (int expression) {         case integer constant value 1:     // entry 1              statement 1;             Statement 2;               Break  ;           Case Integer constant value 2:     // entry 2              statement 3;               Break  ;             ...          Default:               // defaults to entry              statement n;}

1 . Integer expression: char, Byte, short, int, and enum JDK 7.0 added string type

2, break function is to jump out of the switch statement, if not encountered break will continue to execute the Next statement:

 int  a=1 switch   (a) { case  0     0 case  1: System.out.println ( 1 Span style= "color: #000000;"    >);  case  2: System.out.println ( 2 Span style= "color: #000000;"        >);     break  ;  case  3: System.out.println ( 3 Span style= "color: #000000;"        >);  break  ;}  

Because A=1, so the entry in case 1: here, so immediately executes the statement System.out.println (1); found there is no break, so continue to execute System.out.println (2); Then exit the switch statement

3, in many cases, switch-case can replace the else if structure, and switch-case to achieve the efficiency of branching function than the else if structure , and the structure is clearer, so it is recommended. Starting with JDK 7.0, switch-case can support string expressions, which will make it easier for the program to operate.

The difference between the three, while and Do-while statements

While is first judged, in execution; Do-while is performed first in judgment. So do-while, in any case, executes more than the while.

Iv. for statement

1. For general wording

　　For (expression 1; expression 2; expression 3 ) {

Statement block

}

For example:

 for (byte i=0;i<100;i++) {    System.out.println (i);}

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2, for the special wording

The first type:

int sum = 0 ; int i = 1;  for (  ; I <=; i + + ) {    + = i;} System.out.println (

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The second type:

int  sum = 0 ;  for int i = 1; I <= ;) {    + = i    ; ++ ;} System.out.println ("1 to 10 and for:" + sum);

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The third type:

 for  (   ;   ;   ) {    System.out.println ("I want to learn ...")

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This method will form a dead loop, and the same effect as while (true)

It is not difficult to see through the above several special wording, expression 1, expression 2 and expression 3 can be omitted, but the semicolon cannot be omitted

The fourth type:

 for int  I =1, j = 6  ;  I <= 6  ;  I +=2, J-=2 ) {    = "+ i +", "+ J");}

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The fifth type:

int [] arr={1,2,3,4,5,6,7,8};  for (int  i:arr) {    System.out.println (i);}

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17. Java Process Control