How to implement an arraylist without using java.util.arraylist?

If you want to see the actual code that each API uses, look inside your JDK folder for the src.zip. Refer to the javadocs of the API to discover the path to the framework you are interested in, e.g. open folders /java/util/ArrayList.java

the difficulty in sorting 'ArrayList' manually is that we ought to write down separate purposes for each records style. basically see the implementation for a 'long' records style: public int median(long x[], int a, int b, int c) { return (x[a] < x[b] ? (x[b] < x[c] ? b : x[a] < x[c] ? c : a) : (x[b] > x[c] ? b : x[a] > x[c] ? c : a)); } public void replace(long x[], int a, int b) { long t = x[a]; x[a] = x[b]; x[b] = t; } public void vectorswap(long x[], int a, int b, int n) { for (int i=0; i<n; i++, a++, b++) replace(x, a, b); } //speedy form implementation of Sorting the records public void form(long x[], int off, int len) { if (len < 7) { for (int i=off; i<len+off; i++) for (int j=i; j>off && x[j-a million]>x[j]; j--) replace(x, j, j-a million); return; } int m = off + (len >> a million); if (len > 7) { int l = off; int n = off + len - a million; if (len > 40) { int s = len/8; l = median(x, l, l+s, l+2*s); m = median(x, m-s, m, m+s); n = median(x, n-2*s, n-s, n); } m = median(x, l, m, n); } long v = x[m]; int a = off, b = a, c = off + len - a million, d = c; on an identical time as(real) { on an identical time as (b <= c && x[b] <= v) { if (x[b] == v) replace(x, a++, b); b++; } on an identical time as (c >= b && x[c] >= v) { if (x[c] == v) replace(x, c, d--); c--; } if (b > c) destroy; replace(x, b++, c--); } int s, n = off + len; s = Math.min(a-off, b-a ); vectorswap(x, off, b-s, s); s = Math.min(d-c, n-d-a million); vectorswap(x, b, n-s, s); if ((s = b-a) > a million) form(x, off, s); if ((s = d-c) > a million) form(x, n-s, s); } Parameters: x[] - array to form --> ArrayList==> obj.toArray() off - Offset --> commencing component in Array from the place sorting starts off (regularly 0). len- length --> form of factors to form from Offset (length()). as a replace of 'long' records style, basically attempt 'merchandise' records style.