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content/ta/spring2018/cpsc220/jan25.md

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+# Lecture for January 25
+
+## Strings
+
+These are concatenated chars
+
+```java
+'d' + 'o' + 'g' // equivalent to "dog"
+```
+
+```java
+"straw" + "berry" // strawberry
+```
+
+Strings are denoted by double quotes `""` rather than a string which is denoted by single quotes `''`
+
+String is not a primitive type, it is a class. Hence, why it is capitalized in Java.
+
+The `java.lang.String` is automatically imported in Java.
+
+To declare and initialize a String
+
+```java
+String name = "Henry";
+```
+
+In memory it appears as
+
+| H    | 'e'  | 'n'  | 'r'  | 'y'  |
+| ---- | ---- | ---- | ---- | ---- |
+|      |      |      |      |      |
+
+### String Methods
+
+```java
+int length()
+```
+
+```java
+boolean equals(String another)
+```
+
+```java
+boolean startsWith(String prefix)
+```
+
+```java
+boolean endsWith(String suffix)
+```
+
+```java
+String substring(int start, int end)
+```
+
+```java
+int indexOf(int ch)
+```
+
+```java
+String toLowerCase()
+```
+
+### Using String Methods
+
+```java
+char first = name.charAt(0);
+```
+
+Remember in Java, that it starts counting from zero! If you try to access a letter that doesn't exist, it will produce an `IndexOutOfBounds` error.
+
+## Errors
+
+There are two types of errors, compile-type errors and run-time errors.  Later we will talk about debugging skills such as making "breakpoints" in your code so you can analyze the different variable values.
+
+### Compile Time Errors
+
+Compile time errors are generated due to syntax errors. Forgot a semicolon? Missing a brace? 
+
+### Run-time Errors
+
+These are logic errors. Not derived from syntax errors. An example of one that was discussed earlier is the `IndexOutOfBounds` error.
+
+
+
+## Tricky Thing About Input
+
+Let's talk about input right now. Let's say you have the following scenario
+
+```java
+Scanner input = new Scanner(System.in);
+System.out.println("Enter pet's age: ");
+int age = input.nextInt();
+System.out.println("Enter pet's name: ");
+String name = input.nextLine();
+System.out.println("Enter pet's breed: ");
+String breed = input.next();
+```
+
+Then when we start to run the program...
+
+```reStructuredText
+Enter pet's age: 
+14
+Enter pet's name:
+Enter pet's breed:
+Labradoodle
+```
+
+Why did it skip pet's name? Let's run through the process again
+
+```reStructuredText
+Enter pet's age: 
+14 [ENTER]
+Enter pet's name:
+Enter pet's breed:
+Labradoodle
+```
+
+Here the [ENTER] key gets saved into name.
+
+To resolve this, just use an `input.nextLine()` to throw away that [ENTER]
+
+```java
+Scanner input = new Scanner(System.in);
+System.out.println("Enter pet's age: ");
+int age = input.nextInt();
+System.out.println("Enter pet's name: ");
+input.nextLine();
+String name = input.nextLine();
+System.out.println("Enter pet's breed: ");
+String breed = input.next();
+```
+
+
+
+
+