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94 lines
2.2 KiB
Markdown
94 lines
2.2 KiB
Markdown
# Lecture for February 20th
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## Reading a File
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You can get input from a file instead of from the terminal
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```java
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FileInputStream fileIn = new FileInputStream("myFile.txt");
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// Our familiar Scanner
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Scanner scnr = new Scanner(fileIn);
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// We can use our usual Scanner methods
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String line = scnr.nextLine();
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fileIn.close(); // Remember to close the file when you're finished with it!
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```
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### Reviewing Scanner Methods
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To understand some of the Scanner methods we need to be aware of the "newline" character. This character is equivalent to the `Enter` button on the keyboard.
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`scnr.nextLine()` This get's all the characters in the buffer up to the newline character.
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`scnr.next()` Grabs the characters in the next "token". Tokens are usually separated by any whitespace type character (spaces, enters, tabs, etc.)
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## Writing to a File
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Prints information to a file instead of to the screen
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```java
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FileOutputStream fileOut = new FileOutputStream("myOutfile.txt");
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PrintWriter out = new PrintWriter(fileOut);
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out.println("Print this as the first line.");
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out.flush(); // Pushes the file changes to the file
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fileOut.close(); // If you forget this then it won't remember your changes
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```
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## Arrays
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Arrays are containers of fixed size. It contains a fixed number of values of the **same type**. (Ex: 10 integers, 2 strings, 5 booleans)
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Declaration
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```java
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int[] array; // This declares an integer array
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```
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Initialization
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```java
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array = new int[7]; // This states that this array can hold up to 7 integers
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```
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Storing a value in an array
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- Square bracket notation is used
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```java
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int[] array = new int[7];
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array[0] = 5; // Stores 5 into the first slot
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```
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Now let us attempt to retrieve the value
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```java
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int temp = array[0];
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System.out.println(temp); // Prints "5"
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```
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### Traversing an Array
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Let's say we have the following array
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```java
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int[] numbers = {3, 5, 2, 7, 9};
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```
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Let's print out each of the values in the array
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```java
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for (int i = 0; i < numbers.length; i++) {
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System.out.print("value in " + i " is " + numbers[i]);
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}
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```
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### Finding the maximum value in an Array
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```java
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int highest = numbers[0];
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for (int i = 0; i < numbers.length; i++) {
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if (numbers[i] > highest) {
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highest = numbers[x];
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}
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}
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```
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