Switch in Java

A switch statement consists of a control expression and multiple case labels.

The types supported by the switch control expressions are byte, short, char, int, enum (Java 5), String (Java 7).

The Switch-case statement can be fully interoperable with the If-else statement, but generally, theswitch-case statement executes more efficiently .

Default is executed when the current switch cannot find a matching case. Default is not a must.

Once the case is matched, the subsequent program code is executed sequentially, regardless of whether the following case matches until a break is encountered.

Usage examples:

1). int type Switch Example

inti = 3;

switch (i) { case 1 :      System.out.println( 1 );      break ; case 2 :      System.out.println( 2 );      break ; case 3 :      System.out.println( 3 );      break ; default :      System.out.println( 0 ); }2). Enum (enum) type switch example public class TestSwitch {      static enum E {          A, B, C, D      }      public static void main(String args[]) {          E e = E.B;          switch (e) {          case A:              System.out.println( "A" );              break ;          case B:              System.out.println( "B" );              break ;          case C:              System.out.println( "C" );              break ;          case D:              System.out.println( "D" );              break ;          default :              System.out.println( 0 );          }      }3). String Type Switch Example

String str = "C";

switch (str) { case "A" :      System.out.println( "A" );      break ; case "B" :      System.out.println( "B" );      break ; case "C" :      System.out.println( "C" );      break ; default :      System.out.println( 0 ); }4). Break Trap: Break is used in switch to end the current process. Once the case is matched, the subsequent program code is executed sequentially, regardless of whether the following case matches until a break is encountered. int i =  2 ; switch (i) { case 1 :      System.out.println( 1 ); case 2 :      System.out.println( 2 ); case 3 :      System.out.println( 3 ); default :      System.out.println( 0 ); }Output Result: 2 3 05).Default:default is executed when the current switch cannot find a matching case. Default is not a must. int x =  0 ; switch (x) { case 1 :      System.out.println( 1 ); case 2 :      System.out.println( 2 ); default :      System.out.println( "default" ); } Precautions1). switch (a), the value of a in parentheses can only be an integer or a numeric type that can be converted to an integral type, such as Byte, short, int, char, and enumeration; It is important to emphasize that long and string types are not java7 before the switch statement. After Java7, string can be used. 2). Case B:c;case is a constant expression, which means that the value of B can only be constant or int, byte, short, char (for example, 1, 2, 3, 200000000000 (note that this is an integer)), If you need to write an expression or a variable here, add a single quotation mark; The statement after the case can be used without curly braces, or C does not have to be wrapped in curly braces;

3). The case must be followed by a constant, and cannot be a long or float type:

private int click_query = 1;

Switch (TAG) {case  click_query:// error, Click_query is not a constant , final decoration, must be a final type constant, not a final variable, for example: final int Click_query = 1; But it cannot be final int click_query;

Query (); Break

4). The range of values following the case:

byte a = one;  Switch (a) {//C case  11:system.out.println ("11"); break;  225 The range of byte is exceeded (the range of byte is -127~128), so an error occurs

Switch in Java