Schlagwort: class

Objektorientierung in JavaScript und Java

Ich habe eine Klasse „Person“ in JavaScript und Java geschrieben, um zu zeigen, wie Namensräume (engl. namespaces) und Objektorientierung in beiden Programmiersprachen aussehen.
Objektorientierung in JavaScript und Java weiterlesen

Converting Java Collections, Array of Wrapper Types and Array of Primitives

With this post I just want to show how to convert a Java collection into an array and how to convert a wrapper class array into an array of the corresponding primitive data type. As a bonus I will show how to iterate over an ArrayList.

Code

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 public static void main(String[] args)
  {
    // Java collection (ArrayList) with Floats
    ArrayList<Float> someFloats = new ArrayList<Float>();
    someFloats.add(3.72f);
    someFloats.add(28.07f);
    someFloats.add(2011f);
    // Convert ArrayList into an array
    Float[] floatWrapperArray = someFloats.toArray(new Float[someFloats.size()]);
    float[] floatArray = new float[floatWrapperArray.length];
    // Transfer array of Wrapper type (Float) into array of primitive data type (float)
    for (int i = 0; i < floatArray.length; i++)
    {
      floatArray[i] = floatWrapperArray[i].floatValue();
    }
    // 1. Float ArrayList
    System.out.println("1. Float ArrayList");
    for (Iterator iterator = someFloats.iterator(); iterator.hasNext();)
    {
      Float currentFloat = (Float) iterator.next();
      System.out.println(currentFloat);
    }
    // 2. Float array
    System.out.println("2. Float array");
    for (int i = 0; i < floatWrapperArray.length; i++)
    {
      System.out.println(floatWrapperArray[i]);
    }
    // 3. float array
    System.out.println("3. float array");
    for (int i = 0; i < floatArray.length; i++)
    {
      System.out.println(floatArray[i]);
    }
  }

Output

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1. Float ArrayList
3.72
28.07
2011.0
2. Float array
3.72
28.07
2011.0
3. float array
3.72
28.07
2011.0