java - Copy Elements From Stack to Queue -
i'm supposed copy elements stack queue.
i haven't been able think of way keep stack way , still copy elements queue.
i ended method removes elements stack , adds them queue:
public void copyfromstack(){ e t; int c = w.size(); while(c != 0){ t = w.pop(); enqueue(t); c--; }} trying push elements not option because it'll backwards.
edit: class contains method queue class:
public class queue<e> { protected int size; protected node<e> head; protected node<e> tail; nodestack<e> w = new nodestack<e>(); nodestack<e> w2 = new nodestack<e>(); public queue(){ size = 0; head = tail = null;} public boolean isempty(){ return size==0;} public void enqueue(e elem) { node<e> node = new node<e>(); node.setelement(elem); node.setnext(null); if (size == 0) head = node; else tail.setnext(node); tail = node; size++; } public e dequeue() { if (size == 0) system.out.print("queue empty."); e tmp = head.getelement(); head = head.getnext(); size--; if (size == 0) tail = null; return tmp; } public string tostring(){ string s = ""; e t; int c = size; while(c != 0){ t = dequeue(); s += t + " "; enqueue(t); c--; } return s;} public int finditem(e elem){ int index=0; int c = size; e t; while(c != 0){ t = dequeue(); if (t == elem) return index; else index++; c--;} system.out.print("not found!"); return -1;} public void copytostack(){ system.out.print("elements copied stack are: "); e t; int c = size; while(c != 0){ t = dequeue(); w.push(t); enqueue(t); c--; system.out.print(w.pop()+" "); }} public void copyfromstack(){ e t; int c = w.size(); while(c != 0){ t = w.pop(); enqueue(t); c--; }}
q: haven't been able think of way keep stack way a:
a: that's because reading "classic" stack destructive. "reading" element == removing element stack.
two solutions:
1) modify stack implementation can "peek" each element
... or ...
2) create new stack containing elements first one.
q: ended method ... trying push elements not option because it'll backwards.
"a: variation on "option 2): above.
solution: create new stack object, , push each element @ same time enqueue element.
ps:
the standard jre implementation of stack includes peek() , search() methods. don't think here. if wanted "option 1)", you'd have implement own, custom stack.
================== update ==================
note, too:
you should indent methods, , indent "if" , "loop" blocks within methods.
you should use "camel-case" (lower-case first letter) method names.
here "official" java coding conventions. useful in 1995; they're useful today:
http://www.oracle.com/technetwork/java/index-135089.html
there's third option: java's "stack" happens implement "iterator". here's example:
example code:
package com.testcopy; import java.util.arraydeque; import java.util.iterator; import java.util.queue; import java.util.stack; public class testcopy { public static void main (string[] args) { testcopy app = new testcopy (); app.run (); } public void run () { // create , populate stack stack<string> mystack = new stack<string> (); mkdata(mystack); // copy queue queue<string> myqueue = new arraydeque<string> (); copyfromstack (mystack, myqueue); // print int i=0; (string s : myqueue) { system.out.println ("myqueue[" + i++ + "]: " + s); } } @suppresswarnings("unchecked") public void mkdata (stack stack) { stack.push("a"); stack.push("b"); stack.push("c"); // stack should contain c, b, } public void copyfromstack (stack stack, queue queue) { @suppresswarnings("rawtypes") iterator = stack.iterator (); while (it.hasnext()) { queue.add(it.next()); } } } example output:
myqueue[0]: myqueue[1]: b myqueue[2]: c
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