primitives, declare instantiate intialize, common imports

This commit is contained in:
Xevion
2020-01-25 04:03:27 -06:00
parent 1ff0a8957b
commit 4212133d45

View File

@@ -252,4 +252,59 @@ In fact, it's likely that aspiring Software Engineers will want to get used to t
{
// print the file
}
}
}
### Most Common Imports
```java
import static java.lang.System.out;
> out.println("shorthand println");
import java.io.File; // Read and Write files
> File input = new File("input1.dat"); // can be thrown directly into a Scanner's input
import java.io.FileNotFoundException;
> public static void main(String[] args ) throws FileNotFoundException {
import java.util.Scanner;
> Scanner s = new Scanner();
> s.nextInt();
> s.hasNextInt();
> s.nextLine();
import java.util.Arrays;
> Arrays.toString(new int[]{});
```
### Declare, Instantiate, Initalize
* Declaration: The code set in bold are all variable declarations that associate a variable name with an object type.
```java
type name;
int age;
double magnitude;
Point origin;
```
* Instantiation: The new keyword is a Java operator that creates the object.
```java
Point origin = new Point();
```
* Initialization: The new operator is followed by a call to a constructor, which initializes the new object. Instantiation and Initalization almost always occur on the same line, in the same instant.
```java
class Point
{
private int x;
private int y;
Point(int x, int y) <--- Initalization
{ <--- is
this.x = x; <--- occurring
this.y = y; <--- right
} <--- here
}
```
### When Primitive Array Casts Are Required
Primitive Arrays can be declared and
```java
int[] myIntArray = new int[3];
int[] myIntArray = {1, 2, 3};
int[] myIntArray = new int[]{1, 2, 3};
```