Java Code

For Loop

When you know exactly how many times you want to loop through a block of code

Ex.

for (int i = 0; i < 5; i++) {
  System.out.println(i);
}

• Statement 1 sets a variable before the loop starts: int i = 0

• Statement 2 defines the condition for the loop to run: i < 5. If the condition is true, the loop will run again; if it is false, the loop ends.

• Statement 3 increases a value each time the code block has run: i++

Output:

0
1
2
3
4

While Loop

Loops can execute a block of code as long as a specified condition is true.

Ex.

the code in the loop will run again and again, as long as a variable (i) is less than 5

int i = 0;
while (i < 5) {
  System.out.println(i);
  i++;
}

Output:

0
1
2
3
4

Conditions and If Statements

let you control the flow of your program - deciding which code runs, and which code is skipped

Conditions:

• Less than: a < b

• Less than or equal to: a <= b

• Greater than: a > b

• Greater than or equal to: a >= b

• Equal to: a == b

• Not equal to: a != b

Ex.

if (20 > 18) {
  System.out.println("20 is greater than 18");
}

If-Else Statements

runs a block of code when the condition in the if statement is false

Ex.

if (20 > x) {
  System.out.println("20 is greater than x");
else
  System.out.println("20 is less than x");
  
}

Comment

explains what your code is doing

Ex.

// This is a comment
System.out.println("Hello World");

Break

terminate a loop (for, while, do-while) or a switch statement

Ex.

for (int i = 1; i <= 10; i++) {
    if (i == 5) {
        break; // Exits the loop when i is 5
    }
    System.out.println(i);
}
// Output:
// 1
// 2
// 3
// 4

Logical Operators

determine the logic between variables or values, by combining multiple conditions

Ex.

• && - and - Returns true if both statements are true

  • x < 5 &&  x < 10

• || - or - Returns true if one of the statements is true

  • x < 5 || x < 4

• ! - not - Reverse the result, returns false if the result is true

  • !(x < 5 && x < 10)

String

contains a collection of characters surrounded by double quotes ("")

Ex.

String greeting = "Hello";