+ – * / % ++ —
++No matter before or after the variable, as long as the + + operation ends, it will automatically add 1
int i = 10; i++; System.out.println(i); // 11 int k = 10; ++k; System.out.println(k); // 11 ++Appear before variable: int i = 10; int k = ++i; System.out.println(k); // 11 System.out.println(i); // 11 ++Appears after variable: int i = 10; int k = i++; System.out.println(k); // 10 System.out.println(i); // 11 int i = 10; System.out.println(i++); // 10 What is the key to solving the above problems? Disassembly code int temp = i++; System.out.println(temp); // 10 System.out.println(i); // 11 int i = 10; System.out.println(++i); Disassembly Code: int temp = ++i; System.out.println(temp); // 11 System.out.println(i); // 11
> >= < <= == !=
The results are Boolean. true/false
& | ! && ||
Logical operators require Boolean types on both sides and the final result is Boolean.
Boolean type on the left & boolean type on the right — > the final result is boolean type.
&Both sides are true, and the result is true
|One side is true, and the result is true
&&In fact, the result is exactly the same as that of & except that & & has short circuit.
When the left is false: & & short circuit.
When the left is true: | short circuit.
= += -= *= /= %=
When using the extended assignment operator, it should be noted that no matter how the operation is performed, the final operation result type will not change.
byte x = 100; // Byte maximum 127 x += 1000; // The compilation can pass. The X variable is still of byte type, but the accuracy is lost. x += 1000; Equivalent to: x = (byte) (x + 1000); int i = 10; i += 10; // Equivalent to: I = I + 10; Add up.
Boolean expression? Expression 1: expression 2
If the Boolean expression is true, select expression 1 as the result.
Conversely, select expression 2 as the result.
String concatenation operator:
+Numbers on both sides, sum.
+There is a string on one side for string splicing.
+If there are multiple, follow the sequence from left to right: 1 + 2 + 3
If you want one of the plus signs to execute first, you can add parentheses: 1 + (2 + 3)
Note: the result after string splicing is still a string.
Tip: how to insert a variable into a string.
String name = "jackson"; System.out.println ("login succeeded, welcome" + name + "back");
How to receive user keyboard input?
java.util.Scanner s = new java.util.Scanner(System.in); //Receive integer int i = s.nextInt() //Receive string String str = s.next();
I recommend you a more detailed Java zero foundation tutorial. The following one I have seen is very good and worth watching and collecting.
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