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72 lines
2.1 KiB
Markdown
72 lines
2.1 KiB
Markdown
# Lecture on March 22nd
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## Method Documentation
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Java has a special way that you can document your methods such that it will create documentation for you if you follow the convention.
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The Java API actually uses this technique to produce its own documentation.
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To create this, indicate a method with special comments that begin with `/**` and ends with `*/`
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It contains *block tags* that describe input and output parameters
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`@param` and `@return`
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### Example
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```java
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/**
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* @param y an integer to sum
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* @param x an integer to sum
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* @return the sum of x and y
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*/
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public int multiply(int x, int y) {
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return x + y;
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}
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```
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## Passing a Scanner
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We only want to create one **user input scanner** per program, we also only want one **file input scanner** per program.
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If a method needs a scanner, you can pass the one you already created in as an input parameter.
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## Array as Input Parameter
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Primitive types (`int`, `char`, `double`, etc.) are passed by value. Modifications made inside a method cannot be seen outside the method.
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Arrays on the other hand, is pass by reference. Changes made to an array inside the method can be seen outside the method.
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```java
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public static void main(String[] args) {
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int[] nums = {1, 3, 5, 7, 9};
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timesTwo(nums);
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}
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public static void timesTwo(int[] arr) {
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for (int i = 0; i < arr.length; i++) {
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arr[i] *= 2;
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}
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}
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```
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At the end of the `timesTwo` method call, the variable `nums` would have `{2, 6, 10, 14, 18}`
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## Sizes of Arrays
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### Perfect Size Arrays
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When we declare an array, Java automatically fills every slot of the array with the type in memory. So if you know that you need exactly 8 slots, then you only ask for 8.
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### Oversize Arrays
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This is when we don't know how many slots we need. Therefore, we ask for more than we think we'll need. That way we don't go out of bounds.
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If we do this, then we don't know how many elements we have already inserted into the array. Since the length is the number of slots.
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So we can create another variable, which will keep track of the index in where we can add the next element.
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We use oversized arrays when the size of the array is unknown or may change.
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