What is Java?:
- Java is a general-purpose, object-oriented programming language
- It is important for our uses as it also powers Android applications
- It is easy to learn, versatile, and well known
Variables:
- Just pieces of information
- Example:
- int number = 120;
- “create an integer variable, ‘number’ and set it to 120”
- int number = 120;
-
- number = 81;
- “reset the previously created variable to 81”
- number++;
- “increase ‘number’ value by 1 (now 82)”
- System.out.print(number);
- “display ‘number’ on the screen”
- number = 81;
Arrays:
- Arrays are similar to variables but store a list of information
- The length of arrays do not change
- Arrays can only hold one data type
- Example:
- public int[] numbers = new int[3];
- “create an integer array ‘numbers’ and set it to a new integer array of size three’
- numbers[2] = 3;
- “reset the value at index 2 of ‘numbers’ to 3”
- *in java the “index” starts at zero, so the value at index 2 is actually the third element in the array (0, 1, 2)
- System.out.println(numbers[2]);
- “display the value at index 2 of ‘numbers’ on the screen”
- public int[] numbers = new int[3];
Loops:
- Allow repeating commands
- A for loop allows you to initiate a counter variable, a check condition, and a way to increment your counter all in one line
for (int i = 0; i < 5; i++){
System.out.print(i);
}
- A while loop is more basic, will evaluate the condition within the brackets, run code, reevaluate condition, so on
while(true){
System.out.print(“hello”);
}
Conditional Statements:
- Conditionals allows the code to make decisions
- Example:
if (name == “Rahul”) {
System.out.print(“Why u sick?”);
}
- Note: && means and, || means not, == means equals?, and != not equals
- Remember == checks equality; = sets equality
Methods:
- A block of reusable code
- Also called functions
- Methods can (but are not required to) take inputs and give outputs
- inputs are called arguments or parameters, and outputs are called returns
- can have mutiple inputs but only 1 output
- Practical Example: think a math function, it takes in a value (x), performs an operation and returns another value (y)
- Examples:
int giveOne() { /* “this function, ‘giveOne,’ will take no inputs and will output an integer value” */
return 1; // “output 1”
} // “we are done with this method”
void print(String text) { /* “this function, ‘print,’ will take a String input but no output” */
System.out.println(text); // “display the inputed text on the screen”
} // “we are done with this method”