Added the solution to the question in Java.

leetCode Solutions/Q8_atoi/Q8_atoi.java

@@ -0,0 +1,25 @@
+/* This solution uses the concept and strings and the functions concerning it. */
+
+Class answer{
+  public int atoi(String s){
+    if(s==null) return 0;     //in case the String is empty
+    s=s.trim();  //removes leading spaces
+    if(s.length()==0) return 0;
+    int sign=-1;
+    long ans=0;   //taking long since integer might exceed the max/min
+    int max=Integer.MAX_VALUE;
+    int min=Integer.MIN_VALUE;
+    if(s.charAt(0)=='-') sign = -1; 
+        int i = (s.charAt(0)=='+' || s.charAt(0)=='-') ? 1 : 0; //skips an index if a sign is there.
+        while(i<s.length()){
+            if(!Character.isDigit(s.charAt(i))) break;    //returns 0 if first index is not a digit and breaks out of the loop.
+            ans = ans * 10 + (s.charAt(i)-'0'); 
+            if(sign == -1 && ans*-1 < MIN) return MIN; //if ans exceeds min then return min according to the question.
+            if(sign == 1 && ans > MAX) return MAX;  //if ans exceeds max then return max according to the question.
+            i++;
+        }
+        return (int)ans*sign;
+  }
+}
+
+