[Add Brick Java] When my classmates went to the toilet between classes, I learned the switch statement.

• content

  Why use switch statement

  Basic syntax of switch statement

  Notes on switch statements

  take a chestnut

  switch triple tap

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• Why use switch statement

• The switch statement provides a workaround for the if statement that selects one of several blocks of statements to execute. The switch statement is Java's multi-way branch statement. It provides an easy way to make different parts of a program execute based on the value of an expression.

• Basic syntax of switch statement

• 

• 1.switch keyword, which means switch branch.
• 2. An expression corresponds to a value.
• 3.case constant 1: When the value of the expression is equal to the constant 1, the statement block 1 is executed.
• 4.break: means to exit the switch.
• 5. If it matches case constant 1, execute statement block 1, if not, match case constant 2.
• 6. If none of them match, execute default.

• Notes on switch statements

• 1. Cases can only be followed by constants, not variables, and the values ​​behind multiple cases cannot appear the same.
• 2. defalut can be omitted but it is generally not recommended to omit.
• 3.break can be omitted, but the running result may not be what we want.
• 4.default can appear anywhere in the switch statement.
• 5. The end condition of the switch statement:
• Execute to the end of the program
• encounter break statement

• take a chestnut

• package demo02;
  import java.util.Scanner;
  public class demo1 {
      public static void main(String[] args) {
      /*
      编写一个程序，这个程序可以接收一个数字，比如1,2,3,4,5,6,7
      1表示星期一，2表示星期二，以此类推
  
       */
          Scanner myscanner = new Scanner(System.in);
          System.out.println("请输入一个数字：");
          int week = myscanner.nextInt();
  
          switch (week) {
              case 1:
                  System.out.println("星期一");
                  break;
              case 2:
                  System.out.println("星期二");
                  break;
              case 3:
                  System.out.println("星期三");
                  break;
              case 4:
                  System.out.println("星期四");
                  break;
              case 5:
                  System.out.println("星期五");
                  break;
              case 6:
                  System.out.println("星期六");
                  break;
              case 7:
                  System.out.println("星期日");
                  break;
              default://如果以上的都没有匹配到就输出default语句
                  System.out.println("输入的数字不正确......");
                  break;
          }
      }
  }
  

• switch triple tap

• 1. Among the following options, which data types can the switch statement judge the condition receive? (ABCD)
• A.int
• B.byte
• C.char
• D.short
• Summary: Java's switch is special, switch only accepts data of int type, then if it receives a low type, it will be turned up to int.
• 2. The following statement about if statement and switch statement is wrong: (D)
• A. Both the if statement and the switch statement can implement the selection structure of the algorithm.
• B. Both the if statement and the switch statement can implement multiplexing.
• C.if statements can be nested.
• D.switch statements cannot be nested.
• 3. In the following switch statement, what types of data can x be: (BDF)

• 

• A.long
• B.char
• C.float
• D.byte
• E.double
• F.String
• Explanation: According to the Java 8-bit standard, switch supports 10 types
• Basic type: byte char short int
• For wrapper class: Byte Short Character lnteger String enum