Java Basic Learning Note 2

Operator:

Emphasis: + + and--operators;

a++ (a--): The first value of a is taken into the calculation, after the calculation is completed, then the value of A is +1 (-1);

++a (--A): First the value of a +1 (-1) operation, and then +1 (-1) after the new a value into the calculation;

Escape characters:

Format: \+ letter or match

In general:

\ nthe line break

\ t tab

\b Backspace key

\ r Press the ENTER key

logical operators

With: &, false on one side, true on both sides;

Or: |, either side is true on both sides and false on both sides;

XOR: ^, with or (|) A bit different: when both sides are true, the result is false----true^true=false

Double and: && When false to the left, no operation is performed on the right.

Double or: | |, when the left is true, no operation is performed on the right.

Bitwise operators: (essentially binary operations, that is, converting the corresponding character numbers into binary operations)

>>: Shift to right gradually decreases. (Divide by 2 to move the number of bits to the power).

<<: Shift to left gradually increases. (multiplied by 2 to move the number of bits to the power).

3 greater than right shift >>>, and the highest bit with 0 complement.

2 greater than number right shift >>, and the highest bit is what is used to complement the position.

Judgment statement:

1 /*2 Requirements: Enter a month to print out the relative seasons and months.3 */4 classIfTest25 {6      Public Static voidMain (string[] args)7     {8         intnum=10;9 Ten         if(num==3| | num==4| | Num==5)  One         { ASystem.out.println (num+ "Month:" + "Spring");  -         }     -         Else if(num==6| | num==7| | Num==8)  the         { -System.out.println (num+ "Month:" + "Summer"); -         } -         Else if(num==9| | num==10| | num==11) +         { -System.out.println (num+ "Month:" + "Autumn"); +         } A         Else if(num==1| | num==2| | Num==12) at         { -System.out.println (num+ "Month:" + "Winter"); -         } -         Else -         { -System.out.println ("Value out of range.")); in         } -  to     } +}

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1 classSwitchdemo2 {3      Public Static voidMain (String args[])4     {5         intA = 2;6         Switch(a)//expressions can only be of these four types: Byte,int,short,char7         {8             //Default:9             //System.out.println ("AAAA"); The default can be placed first, but it is still the last execution.Ten              Case1: OneSystem.out.println ("a"); A                  Break; -              Case2: -System.out.println ("B"); the                  Break; -              Case3: -System.out.println ("C"); -                  Break; +              Case4: -System.out.println ("D"); +             default: ASystem.out.println ("Over"); at                  Break;//can be omitted. -         } -     } -}

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1 /*2 Requirements: Write the month of the user input with switch and print out the season and month.3 */4 classswitchtest5{ Public Static voidMain (String args[])6     {7         intnum = 1;8         Switch(num)9         {Ten              Case3: One              Case4: A              Case5: -System.out.println (num+ "Month:" + "Spring"); -                  Break; the              Case6: -              Case7: -              Case8: -System.out.println (num+ "Month:" + "Summer"); +                  Break; -              Case9: +              Case10: A              Case11: atSystem.out.println (num+ "Month:" + "Autumn"); -                  Break; -              Case12: -              Case1: -              Case2: -System.out.println (num+ "Month:" + "Winter"); in                  Break; -             default: toSystem.out.println ("Month out of range.")); +         } -     } the}

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Java Basic Learning Note 2