1. Create a new class named ArrayLength and add the following code.

public class ArrayLength{
  public static void main(String[] args){
    double[] a = {1.0,2.0,3.0,4.0};
    double[] b = new double[a.length];
    for (int i = 0; i < a.length;i++){
      b[i] = a[i];
    }
    for(int j = 0; j < b.length;j++){
      System.out.println("a[" + j + "]=" + a[j] + " b[" + j + "]=" + b[j]);
    }
  }
}

2. Compile and run the program.

$ javac ArrayLength.java 
$ java ArrayLength
a[0]=1.0 b[0]=1.0
a[1]=2.0 b[1]=2.0
a[2]=3.0 b[2]=3.0
a[3]=4.0 b[3]=4.0

3. Add the following two lines to the end of main.

double[] c = Arrays.copyOf(a, a.length);
System.out.println(Arrays.toString(c));

4. Import java.util.Arrays at the top of the class.

import java.util.Arrays;

5. Compile and run the program.

$ javac ArrayLength.java 
$ java ArrayLength
a[0]=1.0 b[0]=1.0
a[1]=2.0 b[1]=2.0
a[2]=3.0 b[2]=3.0
a[3]=4.0 b[3]=4.0
[1.0, 2.0, 3.0, 4.0]

The complete class should appear as follows.

import java.util.Arrays;

public class ArrayLength{
  public static void main(String[] args){
    double[] a = {1.0,2.0,3.0,4.0};
    double[] b = new double[a.length];
    for (int i = 0; i < a.length;i++){
      b[i] = a[i];
    }
    for(int j = 0; j < b.length;j++){
      System.out.println("a[" + j + "]=" + a[j] + " b[" + j + "]=" + b[j]);
    }
    double[] c = Arrays.copyOf(a, a.length);
    System.out.println(Arrays.toString(c));
  }
}