Java StringBuilder Demystified

import java.util.Arrays; public class MyStringBuilder { private static final int INIT_CAPACITY = 16; private static final float LOAD_FACTOR = 0.75f; private static final int MULTIPLIER = 2; private int currentCapacity = INIT_CAPACITY; // store the total number of characters in our string builder private int count; // storage area for our characters private char[] chars; public MyStringBuilder() { chars = new char[INIT_CAPACITY]; } public MyStringBuilder(String str) { this(); append(str); } public MyStringBuilder append(String newStr) { final int length = newStr.length(); // check if resized or not boolean inflated = ensureCapacity(length); if (inflated) { final char[] newBuffer = new char[currentCapacity]; // copy current content System.arraycopy(chars, 0, newBuffer, 0, count); // copy new content System.arraycopy(newStr.toCharArray(), 0, newBuffer, count, length); // update the store array chars = newBuffer; } else { // add the new content to the remaining array space System.arraycopy(newStr.toCharArray(), 0, chars, count, length); } // update the count of chars count += length; return this; } private boolean ensureCapacity(int newLength) { boolean isInflated = false; // ensure the new length is properly accommodated while (Float.compare((float) (count + newLength) / currentCapacity, LOAD_FACTOR) >= 0) { currentCapacity *= MULTIPLIER; isInflated = true; } return isInflated; } public int length() { return count; } @Override public String toString() { return new String(Arrays.copyOfRange(chars, 0, count)); } } public class MyStringBuilderDriver { public static void main(String[] args) { var sb = new MyStringBuilder(); sb.append("Hi").append(" "); sb.append("Saurabh").append(",").append(" "); sb.append("how are you today ?"); System.out.println(sb); System.out.println(sb.length()); } }