How to create an append method for a char array in Java

I'm currently working on a project for a class to create a TextLine class that represents the a line of text that must be represented as an array of characters.

For one of the methods, I am supposed to take in a string as an argument of a parameter and then append that string to my already created char array.

I was trying to search online for how I could do this, or even an example of the String or StringBuffer class that showed the implementation, but due to my novice skills at Google, I couldn't really find anything useful.

What I 'm thinking is that I first have to convert the string to the array, and then somehow using one of the array methods to add each char individually to the char array.

This is what I have:

public void append(String fragment){

    char[] temp = fragment.toCharArray();

}

I'm not quite sure what array method could b开发者_如何学编程e used, if there even is one. Could someone please help me?

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Normally you would use a StringBuilder as the internal storage for your class but i assume that you need the basic details of how to do this.

The basic process is like this:

• allocate a new array with the size of old array + size of the new data
• copy the old data into the new array
• copy the new data at the end of the new array
• set this as the actual data

Here is the code (this assumes that the data member is declared like this: char[] data = new char[0]:

    public void append(String fragment) {
       char[] fragmentChars = fragment.toCharArray();
       char[] newData = new char[data.length + fragmentChars.length];

       System.arraycopy(data, 0, newData, 0, data.length);
       System.arraycopy(fragmentChars, 0, newData, data.length, fragmentChars.length);

       data = newData;
   }

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Let's say your original char[] array is called arr. Then you can do:

public void append(String fragment){
    arr = (new String(arr)+fragment).toCharArray();
}

This converts your char[] array into a String so you can simply concatenate that to fragment using the + operator. Then you simply convert the new String back to a char[] array using toCharArray().

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You can use the System.arraycopy method to copy the contents of one array into another array. I'll leave it as an exercise to figure out the details.

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As an alternative, you can try a slightly more straightforward method:

public class Test{
char[] arr;

public static void main(String[] args){
    Test t = new Test();
    t.arr = "hi ".toCharArray();
    t.append(" and bye");
    System.out.print(new String(t.arr));
}

public void append(String myString){
    char[] toAppend = myString.toCharArray();
    char[] newArr = new char[toAppend.length+arr.length];
    for(int i = 0; i < arr.length; i++)
        newArr[i] = arr[i];
    for(int i = 0; i < toAppend.length-1; i++)
        newArr[i+arr.length] = toAppend[i];
    arr = newArr;
}
}