Java Derusting

src/ArrayPractice.java

@@ -1,22 +1,36 @@
 public class ArrayPractice {
   public static void main(String[] args) {
     // Create an array of Strings of size 4
-
+    String[]myArray;
+    myArray = new String[4];
     // Set the value of the array at each index to be a different String
     // It's OK to do this one-by-one
+
+    myArray[0] = "Green River";
+    myArray[1] = "Seattle Central";
+    myArray[2] = "Highline";
+    myArray[3] =  "South Seattle";
 
     // Get the value of the array at index 2
+    System.out.println(myArray[2]);
 
     // Get the length of the array
+    System.out.println(myArray.length);
 
     // Iterate over the array using a traditional for loop and print out each item
-
+ for (int i =0; i<myArray.length; i++){
+   System.out.println("Element at index " + i + ": " +myArray[i]);
+ }
     // Iterate over the array using a for-each loop and print out each item
-
+   for (String myArray1 : myArray ){
+    System.out.println(myArray1);
+   }
+
+   }
     /*
      * Reminder!
      * 
      * Arrays start at index 0
      */
   }
-}
+

src/ListPractice.java

@@ -1,28 +1,49 @@
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+
 public class ListPractice {
 
 
   public static void main(String[] args) {
     // Create an empty ArrayList of Strings and assign it to a variable of type List
+     List<String>list = new ArrayList<>();
 
     // Add 3 elements to the list (OK to do one-by-one)
-
+    list.add("Ebtisam");
+    list.add("Manar");
+    list.add("Afnan");
+    list.set(1,"Semah");
+    list.add(0,"Abdulaziz");
     // Print the element at index 1
-
+   System.out.println(list.get(1));
     // Replace the element at index 1 with a new value
+    //I used the set method to replace the list with new value.
+    System.out.println(list);
     // (Do not insert a new value. The length of the list should not change)
 
     // Insert a new element at index 0 (the length of the list will change)
-
+    // I used add method to add the element.
     // Check whether the list contains a certain string
-
+    System.out.println("Contains a certain string manar :" + list.contains("manar"));
+
     // Iterate over the list using a traditional for-loop.
     // Print each index and value on a separate line
+    for (int i =0; i<list.size(); i++){
+      System.out.println( ( "index:" +"["+ i+"]"  )+list.get(i) );
+    }
+
 
     // Sort the list using the Collections library
+   Collections.sort(list);
+   System.out.println(list);
 
+
     // Iterate over the list using a for-each loop
     // Print each value on a second line
-
+    for (String i: list){
+      System.out.println(i);
+    }
     /*
      * Usage tip!
      * 

src/MapPractice.java

@@ -1,30 +1,50 @@
-
+import java.util.HashMap;
+import java.util.Map;
 
 public class MapPractice {
   public static void main(String[] args) {
     // Create a HashMap with String keys and Integer values and
     // assign it to a variable of type Map
+    Map<String, Integer> people = new HashMap<>();
 
     // Put 3 different key/value pairs in the Map
     // (it's OK to do this one-by-one)
 
+     people.put("Manar", 10);
+     people.put("Afnan", 6);
+     people.put("Semah", 4);
+
     // Get the value associated with a given key in the Map
+    for(String i:people.keySet() ){
+      System.out.println("key: " + i + " value: " + people.get(i));
+    }
 
     // Find the size (number of key/value pairs) of the Map
+    System.out.println(people.size());
 
     // Replace the value associated with a given key (the size of the Map shoukld not change)
-
+    String  keyToReplace ="Afnan";
+    Integer newValue = 5;
+    people.replace(keyToReplace,newValue);
+    System.out.println(people);
     // Check whether the Map contains a given key
-
+    System.out.println("Is the given key Semah present?" + people.containsKey("Semah"));
     // Check whether the Map contains a given value
+    System.out.println("Is the given value 3 present?" + people.containsValue(3));
 
     // Iterate over the keys of the Map, printing each key
-
+    for(String name: people.keySet()){
+      System.out.println("key:" + name);
+    }
     // Iterate over the values of the map, printing each value
-
+    for(Integer age: people.values()){
+      System.out.println("valu:" + age);
+    }
     // Iterate over the entries in the map, printing each key and value
-
-    /*
+    for(String i: people.keySet()){
+      Integer age = people.get(i);
+    System.out.println("key: " + i + " valu: " + age);
+    }/*
      * Usage tip!
      * 
      * Maps are great when you want a specific key to value mapping.

src/NumberPractice.java

@@ -1,18 +1,32 @@
 public class NumberPractice {
   public static void main(String args[]) {
     // Create a float with a negative value and assign it to a variable
-
+    float myFloat = -6.1f;
+    System.out.println(myFloat);
     // Create an int with a positive value and assign it to a variable
-
+    int myInt = 250;
+    System.out.println(myInt);
     // Use the modulo % operator to find the remainder when the int is divided by 3
-
+    int a = 8;
+    int b = 3;
+    int x = a%b;
+    System.out.println(x);
     // Use the modulo % operator to determine whether the number is even
     // (A number is even if it has a remainder of zero when divided by 2)
     // Use an if-else to print "Even" if the number is even and "Odd"
     // if the number is odd.
+    if (a % 2 == 0){
+      System.out.println(a + " Even");
+    }else{
+      System.out.println(a + " Odd");
+    }
+
 
     // Divide the number by another number using integer division
-
+    int c = 18;
+    int d = 5;
+    int y =c/d ;
+    System.out.println(y);
     /*
      * Reminder!
      * 

src/Person.java

@@ -5,12 +5,15 @@
 
 public class Person {
   // Declare a public String instance variable for the name of the person
-  // Declare a private int instance variable for the age of the person
-
-
-  // Create a constructor that takes the name and age of the person
-  // and assigns it to the instance variables
-
+   public String name;
+ // Declare a private int instance variable for the age of the person
+   private int age;
+
+
+    // Create a constructor that takes the name and age of the person
+    // and assigns it to the instance variables
+    this.name = personname;
+    this.age= personage;
 
   // Create a toString method that gives the name and age of the person
 

src/SetPractice.java

@@ -1,18 +1,30 @@
+import java.util.HashSet;
+
 public class SetPractice {
   public static void main(String[] args) {
     // Create a HashSet of Strings and assign it to a variable of type Set
-
+    HashSet <String> schools = new HashSet<>(); 
     // Add 3 elements to the set
     // (It's OK to do it one-by-one)
+    schools.add("Green River");
+    schools.add("Seattle Central");
+    schools.add("lake youngs");
+    System.out.println(schools);
+
 
     // Check whether the Set contains a given String
+    System.out.println(schools.contains("Green River"));
 
     // Remove an element from the Set
+    System.out.println(schools.remove("Seattle Central"));
 
     // Get the size of the Set
+    System.out.println(schools.size());
 
     // Iterate over the elements of the Set, printing each one on a separate line
-
+     for (String i : schools){
+      System.out.println(i);
+     }
     /*
      * Warning!
      * 

src/StringPractice.java

@@ -1,20 +1,33 @@
+import java.util.ArrayList;
+
 public class StringPractice {
   public static void main(String[] args) {
     // Create a string with at least 5 characters and assign it to a variable
-
+    String message = "Struggle Coding";
+    System.out.println(message);
     // Find the length of the string
+    System.out.println(message.length());
 
     // Concatenate (add) two strings together and reassign the result
-
+     String message1= "Happy";
+     String message2= "Friday!";
+     String message3 =message1 + message2;
+     System.out.println(message3);
     // Find the value of the character at index 3
 
+    System.out.println(message3.indexOf("p"));
     // Check whether the string contains a given substring (i.e. does the string have "abc" in it?)
-
+    System.out.println(message3.contains("abc"));
     // Iterate over the characters of the string, printing each one on a separate line
-
+   x = message + message3;
+    System.out.println(x);
+
+
     // Create an ArrayList of Strings and assign it to a variable
-
+    ArrayList<String> colors = new ArrayList<>();
     // Add multiple strings to the List (OK to do one-by-one)
+    colors.add ("Red");
+     colors.add ("Brown");
 
     // Join all of the strings in the list together into a single string separated by commas
     // Use a built-in method to achieve this instead of using a loop