Java Array Declarations

1. Can the following be declared with arrays in Java?
   

   int [][] globalArray = new int [3][];
   

   
   
   Answer:
   Yes. As a counter example the following line of code is incorrect and will result in a compiler error.
   

   int [][] array1 = new int[][];
   

   
   A minimum of 1 dimension is required when declaring arrays in Java.

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2. Write a Java constructor that accepts 2 array arguments.
   
   Answer:
   

   public class ArrayDemo {
    private int[] num1 = new int[3];
    private int[] num2 = new int[3];
    public ArrayDemo() { };
    public ArrayDemo(int[] array1, int[] array2) {
     this.num1 = array1;
     this.num2 = array2;
    }
    // ----- main
    public static void main(String[] args) {
     ArrayDemo ad1 = new ArrayDemo(new int[] {1,2,3} ,new int[] {1,2,3} );
    }
   }
   

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3. Can a constructor in Java take one or more arrays as parameters when an object is instantiated?
   
   Answer:
   
   Yes, a constructor in Java can take one or more arrays as parameters when an object is instantiated. This allows the constructor to receive and process arrays during object creation.
   Example: Passing a Single Array to a Constructor

   class Student {
       private int[] scores;
   
       // Constructor accepting an array
       public Student(int[] scores) {
           this.scores = scores;
       }
   
       public void displayScores() {
           for (int score : scores) {
               System.out.print(score + " ");
           }
           System.out.println();
       }
   }
   
   public class Test {
       public static void main(String[] args) {
           int[] marks = {90, 85, 88, 92};
           Student student = new Student(marks);
           student.displayScores();  // Output: 90 85 88 92
       }
   }
   

   
   Here, the constructor "accepts an integer array" and assigns it to the instance variable.
   Example: Passing Multiple Arrays to a Constructor
   

   class Employee {
       private String[] names;
       private double[] salaries;
   
       // Constructor accepting multiple arrays
       public Employee(String[] names, double[] salaries) {
           this.names = names;
           this.salaries = salaries;
       }
   
       public void displayEmployees() {
           for (int i = 0; i < names.length; i++) {
               System.out.println(names[i] + " earns $" + salaries[i]);
           }
       }
   }
   
   public class Test {
       public static void main(String[] args) {
           String[] employees = {"Alice", "Bob", "Charlie"};
           double[] salaries = {50000.0, 60000.0, 55000.0};
   
           Employee emp = new Employee(employees, salaries);
           emp.displayEmployees();
       }
   }
   

   
   Here, the constructor accepts two arrays (`String[]` and `double[]`), and the object processes both.
   Key Points

   1. Any type of array can be passed (primitive or reference types).
   2. Multiple arrays can be passed as parameters.
   3. Arrays are passed by reference, meaning modifications inside the constructor affect the original array.



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4. What are arguments when calling a method?
   
   Answer:
   Arguments are the elements you specify between the parentheses when you are invoking a method. The parameters are the elements in the methods signature.

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5. What is static import?
   
   Answer: static import enables access to static members of a class without need to qualify it by the class name.

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6. How can you think of each of the elements in the primeArray?
   

   int [][] primeArray = {{1,3,5}, { 7,11,13}, { 17, 19, 23}};
   

   
   
   Answer:
   Each of the 3 elements in the primeArray is a reference variable to an int array.

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7. How do you create an anonymous array in Java.
   
   Answer:
   

   class AnonymousArray{
    static void print(int a[]) {
     for(int i=0;i<a.length;++i)
      System.out.print(a[i]+" ");
    }
    
    static void print(int a[][]) {
     for(int i=0;i<a.length;++i){
      for(int j=0;j<a[i].length;++j)
       System.out.print(a[i][j]+" ");
      System.out.println("");
     }
    }
    

   
   

    public static void main(String...s){
     //1d anonymous array 
     print(new int[]{11,23,31,43});
     System.out.println("\n Anonymous Array");
     //2d anonymous array 
     print(new int[][]{{2,3},{5,7},{11,13}});  
    }
   }
   




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8. How can you create an anonymous array for an array of int?
   
   Answer:
   

   int[] testScores;
   testScores = new int[] {4,7,2};
   

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9. Which primitive datatypes can an array of int hold?
   
   Answer:
   a) byte b) char c) short.

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10. What types of data can be assigned to an array?
    
    Answer:
    Any object that passes the "IS-A" test for the declared array type can be assigned to an element of that array.