CSE 3302Lecture'13:'Control9'Mar'2010Nate'NystromUniversity'of'Texas'at'ArlingtonMonday, March 22, 2010Gotogoto'L''––'transfer'control'to'the'statement'labeled'Lunrestricte d'control'flow2Monday, March 22, 2010Goto considered harmfulSpagheH'code:int$n$=$0;while$(1)${$$$$if$(n$<=$10)$goto$A;$else$goto$B;$$$$C:$$$$n++;}B:return$n;A:printf(“%d\n”,$n);goto$C;3Monday, March 22, 2010Structured programming1960swhile'loopsdo'loopsfor'loopsifJthenJelsestatement'blocks4Monday, March 22, 2010Break and continueBreak◾leave'the'current'loop,'resume'aNer'the'loopConOnue◾leave'the'current'loop'iteraOon,'resume'at'to p'o f'lo op5Monday, March 22, 2010For loopsPascal:for$x$:=$1$to$10$do$$$$writeln(x)C:for$(x$=$1;$x$<$10;$x++)$$$$printf(“%d\n”,$x);6Monday, March 22, 2010IterationList<String>$counting$=$$$$Arrays.asList(“yan”,$“tan”,$“tethera”,$“methera”,$“pip”);for$(int$i$=$0;$i$<$counting.size();$i++)${$$$$String$s$=$counting.get(i);$$$$println(s);}7Monday, March 22, 2010Java iteratorsList<String>$counting$=$$$$Arrays.asList(“yan”,$“tan”,$“tethera”,$“methera”,$“pip”);for$(String$s$:$counting)${$$$$println(s);}8Monday, March 22, 2010Java iteratorsList<String>$counting$=$$$$Arrays.asList(“yan”,$“tan”,$“tethera”,$“methera”,$“pip”);for$(String$s$:$counting)${$$$$println(s);}shorthand'for:for$(Iterator<String>$i$=$counting.iterator();$i.hasNext();$)${$$$$String$s$=$i.next();$$$$println(s);}9Monday, March 22, 2010Java iteratorsUsing'iterators'is'easy.How'about'wriOng'one?10Monday, March 22, 2010Writing a Java iteratorImplement'java.uOl.Iteratorinterface'Iterator<T>'{''''boolean'hasNext();''''T'next();}11Monday, March 22, 2010Writing a Java iteratorclass$ArrayListIterator<T>${$$$$ArrayList<T>$list;$$$$int$pos$=$0;$$$$boolean$hasNext()${$return$pos$<$list.size();$}$$$$T$next()${$$$$$$$$if$(pos$<$list.size())${$$$$$$$$$$$$pos++;$return$list.get(posR1);$$$$$$$$}$$$$$$$$else$throw$new$NoSuchElementException();$$$$}}12Monday, March 22, 2010Writing a Java iteratorclass$TreeSet<T>${$$$$$TreeNode<T>$root;$$$$$class$TreeNode<T>${$TreeNode<T>$left,$right;$T$value;$}}class$TreeIterator<T>${$$$$TreeSet<T>$tree;$$$$Stack<TreeNode<T>>$stack;$$$$void$pushLeft(TreeNode<T>$n)${$$$$$$$$if$(n$!=$null)$stack.push(n);$pushLeft(n.left);$}$$$${$pushLeft(tree.root);$}$$$$boolean$hasNext()${$return$!$stack.isEmpty();$}$$$$T$next()${$$$$$$$$TreeNode<T>$x$=$stack.pop();$$$$$$$$pushLeft(x.right);$$$$$$$$return$x.value;$$$$}}13Monday, March 22, 2010Writing a Java iteratorIterator'needs'to'maintain'state◾what'have'I'already'returned?◾what'do'I'return'when'next'invoked?14Monday, March 22, 2010Hashtable'iteratorWhat'bucket'am'I'currently'in?Where'in'the'bucket'am'I?15Monday, March 22, 2010A better way16Monday, March 22, 2010Coroutine iteratorsclass$ArrayList<T>${$$$$T[]$array;$$$$Iterator<T>$iterator()${$$$$$$$$for$(int$i$=$0;$i$<$size;$i++)${$$$$$$$$$$$$yield$array[i];$$$$$$$$}$$$$}}for$(T$x$:$list)${$$$$println(x);}17Monday, March 22, 2010class$ArrayList<T>${$$$$T[]$array;$$$$Iterator<T>$iterator()${$$$$$$$$for$(int$i$=$0;$i$<$size;$i++)${$$$$$$$$$$$$yield$array[i];$$$$$$$$}$$$$}}for$(T$x$:$list)${$$$$println(x);}yield'suspends'the'iterator,'returns'control'back'to'the'caller'(for)When'iterator'next'invoked,'resume'aNer'the'previous'yield'18Monday, March 22, 201019for$(int$i$=$0;$i$<$size;$i++)${$$$$yield$array[i];}for$(String$s$:$counting)${$$$$println(s);}List<String>$counting$=$$$$Arrays.asList(“yan”,$“tan”,$“tethera”,$“methera”,$“pip”);$$$$$Monday, March 22, 201020for$(int$i$=$0;$i$<$size;$i++)${$$$$yield$array[i];}for$(String$s$:$counting)${$$$$println(s);}List<String>$counting$=$$$$Arrays.asList(“yan”,$“tan”,$“tethera”,$“methera”,$“pip”);i$=$0Monday, March 22, 201021for$(int$i$=$0;$i$<$size;$i++)${$$$$yield$array[i];}for$(String$s$:$counting)${$$$$println(s);}List<String>$counting$=$$$$Arrays.asList(“yan”,$“tan”,$“tethera”,$“methera”,$“pip”);i$=$0Monday, March 22, 201022for$(int$i$=$0;$i$<$size;$i++)${$$$$yield$array[i];}for$(String$s$:$counting)${$$$$println(s);}List<String>$counting$=$$$$Arrays.asList(“yan”,$“tan”,$“tethera”,$“methera”,$“pip”);i$=$0Monday, March 22, 201023for$(int$i$=$0;$i$<$size;$i++)${$$$$yield$array[i];}for$(String$s$:$counting)${$$$$println(s);}List<String>$counting$=$$$$Arrays.asList(“yan”,$“tan”,$“tethera”,$“methera”,$“pip”);i$=$0yanMonday, March 22, 201024for$(int$i$=$0;$i$<$size;$i++)${$$$$yield$array[i];}for$(String$s$:$counting)${$$$$println(s);}List<String>$counting$=$$$$Arrays.asList(“yan”,$“tan”,$“tethera”,$“methera”,$“pip”);i$=$0yanMonday, March 22, 201025for$(int$i$=$0;$i$<$size;$i++)${$$$$yield$array[i];}for$(String$s$:$counting)${$$$$println(s);}List<String>$counting$=$$$$Arrays.asList(“yan”,$“tan”,$“tethera”,$“methera”,$“pip”);i$=$1yanMonday, March 22, 201026for$(int$i$=$0;$i$<$size;$i++)${$$$$yield$array[i];}for$(String$s$:$counting)${$$$$println(s);}List<String>$counting$=$$$$Arrays.asList(“yan”,$“tan”,$“tethera”,$“methera”,$“pip”);i$=$1yanMonday, March 22, 201027for$(int$i$=$0;$i$<$size;$i++)${$$$$yield$array[i];}for$(String$s$:$counting)${$$$$println(s);}List<String>$counting$=$$$$Arrays.asList(“yan”,$“tan”,$“tethera”,$“methera”,$“pip”);i$=$1yanMonday, March 22, 201028for$(int$i$=$0;$i$<$size;$i++)${$$$$yield$array[i];}for$(String$s$:$counting)${$$$$println(s);}List<String>$counting$=$$$$Arrays.asList(“yan”,$“tan”,$“tethera”,$“methera”,$“pip”);i$=$1yantanMonday, March 22, 201029for$(int$i$=$0;$i$<$size;$i++)${$$$$yield$array[i];}for$(String$s$:$counting)${$$$$println(s);}List<String>$counting$=$$$$Arrays.asList(“yan”,$“tan”,$“tethera”,$“methera”,$“pip”);i$=$1yantanMonday, March 22, 201030for$(int$i$=$0;$i$<$size;$i++)${$$$$yield$array[i];}for$(String$s$:$counting)${$$$$println(s);}List<String>$counting$=$$$$Arrays.asList(“yan”,$“tan”,$“tethera”,$“methera”,$“pip”);i$=$2yantanMonday, March 22, 201031for$(int$i$=$0;$i$<$size;$i++)${$$$$yield$array[i];}for$(String$s$:$counting)${$$$$println(s);}List<String>$counting$=$$$$Arrays.asList(“yan”,$“tan”,$“tethera”,$“methera”,$“pip”);i$=$2yantanMonday, March 22,
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