Typical Recursion Example (hanoi problem)

public void move(int n, String strFrom, String strTemp, String strTo) {if (n == 1) {show(1, strFrom, strTo);} else {move(n - 1, strFrom, strTo, strTemp);move(n - 1, strTemp, strFrom, strTo);}}

Then I come cross the term recursion and tail recursion in Erlang.

%% recursion
sum([H|T]) ->H + sum(T);
sum([]) ->0.

%% tail recurion
sum(X) ->sum(X, 0).
sum([H|T], Acc) ->sum(T, H + Acc);
sum([], Acc) ->Acc.

What is A Tail Call?

A tail call is a fancy term that refers to a situation in which a method or function call is the last instruction inside of another method or function.

Recursion Code with Java.

     /*** sum from 1 to n. recursion* @param i* @return sum */public int recur_head(int i){if(i==1)return 1;elsereturn i+recur_head(i-1);}

Tail Recursion Code with Java.

    /**** sum from 1 to n. tail recursion* @param i* @param total* @return*/public int recur_tail(int i, int total){if (i == 1)return 1+total;return recur_tail(i-1, total +i);}

See the class with

 javap -c

public class Recur {public Recur();Code:0: aload_01: invokespecial #1                  // Method java/lang/Object."<init>":()V4: returnpublic int recur_head(int);Code:0: iload_11: iconst_12: if_icmpne     75: iconst_16: ireturn7: iload_18: aload_09: iload_110: iconst_111: isub12: invokevirtual #2                  // Method recur_head:(I)I15: iadd16: ireturnpublic int recur_tail(int, int);Code:0: iload_11: iconst_12: if_icmpne     95: iload_26: iconst_17: iadd8: ireturn9: aload_010: iload_111: iconst_112: isub13: iload_214: iload_115: iadd16: invokevirtual #3                  // Method recur_tail:(II)I19: ireturn
}

for Java Developer

Java programmers tend to avoid recursion through the use of loops.

int factorial(int n) {int result = 1;for (int t=n; t > 1; t--)result *= t;return result;}

Reference

http://www.drdobbs.com/jvm/tail-call-optimization-and-java/240167044