Learning Java. I will make a note so that I can look back on it for review. It's almost my study memo. Please do not excessive expectations.
--if statement
The if statement means "if-if" in English, and the part corresponding to this "-" is the part in () after the if. This is called a conditional expression. If the conditional expression is true, the processing inside {} is performed, and if the conditional expression is false, nothing is done.
Conditional expressions include "true / false value" and "comparison operator (==, <Etc.) ”,“ Logical operators (&&, ||, !) ”Is utilized. No semicolon is required after {}.
How to write
if(Conditional expression){
//Processing content;
}
Example
//Definition of variables of integer type
int x = 5;
//Using an if statement, output "x is greater than 2" when the variable x is greater than 2.
if(x > 2) {
System.out.println("x is greater than 2");
}
Output result
x is greater than 2
-else、 else if
else means "other" in English, and if you combine if and else, Conditional branching of "If ..., then ◯◯, otherwise △△" is possible.
Furthermore, by using else if, further conditional branching becomes possible. By combining if, else if, and else, It is possible to realize a conditional branch such as "If ... then ◯◯, if not XX then △△, if neither is □□".
Example
//Definition of variables of integer type
int number = 12;
//Conditional branching that combines if, else if, and else
if (number < 10) {
System.out.println("Less than 10");
}else if(number < 20){
System.out.println("10 or more, less than 20");
}else{
System.out.println("over 20");
}
Output result
10 or more, less than 20
--switch statement
Conditional branching also has a syntax called a switch statement. The switch statement is processed when the condition value matches the case value. Also, break is an instruction to end the switch statement. If there is no break, after processing the matching case, the processing of the next case will also be executed. Unintended processing will occur.
Note that the colon (:) after the case is easy to forget.
How to write
switch(Condition value){
case value 1:
//Processing content;
break;
case value 2:
//Processing content;
break;
case value 3:
//Processing content;
break;
}
Example
int number = 12;
switch(number%3) {
case 0:
System.out.println("Dividable by 3");
break;
case 1:
System.out.println("Divide by 3 to get 1 remainder");
break;
case 2:
System.out.println("Divide by 3 to get 2");
break;
}
Output result
Dividable by 3
In the switch statement, the process to be executed when it does not match any case can be specified in default.
This is similar to the else of an if statement.
Example
int number = 18;
switch(number%5) {
case 0:
System.out.println("Dividable by 5");
break;
case 1:
System.out.println("Divide by 5 to get 1 surplus");
break;
case 2:
System.out.println("Divide by 5 to get 2");
break;
default:
System.out.println("other than that");
break;
}
Output result
other than that
--while statement
while is an English word meaning "between", and the while statement is " repeat the process in {} while the condition is true "
Can be done.
How to write
while(conditions){
//Repeated processing;
}
How to write
int number = 10; //①
//Create an iterative process that repeats when number is greater than 0 using a while statement
while(number > 0){ //②
System.out.println(number); //③
number-=1; //④
}
① Variable initialization ↓ ② Conditions ↓ ③ Repeated processing ↓ ④ Variable update ↓ ② Conditions ↓ ③ Repeated processing ↓ ④ Variable update
--for statement
The for statement is also one of the iterative processes.
In the for statement, describe the three " variable initialization, conditional expression, variable update " in () after for.
Separate each with a semicolon (;), but note that the last variable update does not have a semicolon (;).
How to write
//Create an iterative process that repeats when number is greater than 0 using a for statement
for(int number = 10; number > 0; number-=1){
System.out.println(number);
}
-break、continue
To end the iterative process, use break instead of setting the condition to false. There is a way to forcibly terminate it.
Example
int i = 1;
//When i is a multiple of 5, iterative processing ends
while (i < 10) {
if(i % 5 == 0){
break;
}
System.out.println(i);
i++;
}
Output result
1
2
3
4
continue can skip only the processing of that lap and execute the next lap.
Example
for (int j = 1; j < 10; j++) {
//Skip processing when j is a multiple of 3
if(j%3==0){
continue;
}
System.out.println(j);
}
Output result
1
2
4
5
7
8
[Java ~ Variable definition, type conversion ~] Study memo [Java ~ False Value ~] Study Memo 2
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