CC3.2.java

public class StackMin{
    private int[] Stk;
    private int top_s;
    private int[] Min;
    private int top_m;
    
    public StackMin() {
        this.Stk = new int[1];
        this.Min = new int[1];
        this.top_s = -1;
        this.top_m = -1;
    }
    
    public void push(int val) {
        resize_if_full();
        Stk[++top_s] = val;
        if(top_m == -1 || val < Min[top_m])
            Min[++top_m] = val;
    }
    
    private void resize_if_full() {
        if(top_s == Stk.length-1) {
            int size = Stk.length;
            int[] temp = new int[size * 2];
            for(int i = 0; i < size; i++)
                temp[i] = Stk[i];
            Stk = temp;
        }
        if(top_m == Min.length-1) {
            int size = Min.length;
            int[] temp = new int[size * 2];
            for(int i = 0; i < size; i++)
                temp[i] = Min[i];
            Min = temp;
        }
    }

    public int pop() {
        if(isEmpty())
            throw new NoSuchElementException("stack underflow!");
        int val = Stk[top_s--];
        if(Min[top_m] == val && Stk[top_s] != val)
            top_m--;
        return val;
    }
    
    private boolean isEmpty() {
        return top_s == -1;
    }

    public int min() {
        if(isEmpty())
            throw new NoSuchElementException("stack underflow!");
        return Min[top_m];
    }
}

1. You can use Stack class from Java instead of creating 2 new arrays.