Break Statement Usage

1
Section 4

• Break Statement Usage
• Integer Class and other Wrapper class
• Inside Object Array
• Remove element from a list
• Recursive approach
• Iterative approach

2
(1) Break Statement Usage

• Loop Break

myArray 1-d integer array for (int i0 i lt
myArray.length i) if (myArrayi
0) break // break out of for
loop // execution resumes at
following statement on break
3
(1) Break Statement Usage

• Label Break

myArray 2-d integer array breakout
for (int i0 i lt myArray.length i)
for (int j0 j lt myArrayi.length j)
if (myArrayij 0)
break breakout // break out of for loop
// execution resumes at
following statement on break
4
(1) Break Statement Usage

• Not recommend label break, not a good programming
  style.
• Label break and loop break can be eliminated.

for (int i0 i lt myArray.length
myArrayi!0 i) // execution resumes
5
(2) Integer class

• int is java built-in primitive data type.
• The Integer class wraps a value of the primitive
  type int in an object.
• An object of type Integer contains a single field
  whose type is int.

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(2) Integer class API

• Create an Integer object.
• Integer IntObj new Integer(5)
• Retrieve an Integer objects value.
• int n IntObj.intValue( )
• Parse a integer from a String.
• int n Interger.parseInt(1234)

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(2) Integer class Class Hierarchy

• Object class is the root of the java class
  hierarchy.

8
(2) Integer class Casting

• Casting ( the same thing with different type)
• Upcasting
• Downcasting

9
(3) Object Array

• Storage Structure
• IntArr, Integer Array with length 3

Heap
Integer1
IntArr
Integer1
Integer1
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(3) Create Object Array

• IntArr new Integer3

Heap
null
IntArr
null
null
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(3) Create Object Array

• IntArr new Integer3
• For(int I0 Ilt3 I) IntArrinew Integer(i)

Heap
Integer1
IntArr
Integer1
Integer1
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(3) Create Object Array

• Summary
• When creating an array of objects, each element
  is a reference variable with a default value of
  null.
• Need to explicitly create an obj for each element.

13
(4) Remove element from list
class ListCell //data protected Object
datum protected ListCell next //methods
public ListCell(Object o, ListCell n)
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(4) Remove list element (Recursion)

1. Assumption List elements are sorting in
   ascending order
2. Example

ListCelll
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listcellDelete(Integer num, ListCell l) if (l
null) return null if (no more smaller
value) return l else suppose l is f,
n if num f return
l.getnext() else
l.setNext( listcellDelete(c, l.getNext()))
return l
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public static ListCell deleteRec(Integer obj,
ListCell l) if (l null) return null int
lvalue((Integer)l.getDatum).intValue() int
ovalueobj.intValue() if (lvalue gt ovalue)
return l / not in list / if (lvalueovalue)
/ delete this cell/ return
l.getNext() l.setNext(deleteRec(obj,
l.getNext())) /delete from the rest of the
list/ return l
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• listcellDelete(Integer num, ListCell l)
• Iterative approach
• Locate the predecessor of the cell that we need
  to delete. (Scan)
• Update the predecessors next pointer point to
  the deleted cells next point.

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public static ListCell deleteIter(Integer obj,
ListCell l) //check three simple cases
first if (l null) return null int
ovalueobj.intValue() if (((Integer)l.getDatum).
intValue()ovalue) return l.getNext()
if (((Integer)l.getDatum).intValue()gtovalue)
return l //Cont
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public static ListCell deleteIter(Integer obj,
ListCell l) //Cont. //current and scout
are cursors into list. //both advance in lock
step, scout is one cell ahead //stop if scout
points to cell containing obj or if scout is
null ListCell current l ListCell scout
l.getNext() while ((scout ! null)
((Integer)scout.getDatum()).intValue() lt
ovalue) current scout scout
scout.getNext() //if scout is not null, we
have found a cell containing obj if (scout !
null ((Integer)scout.getDatum()).intValue()
ovalue)) current.setNext(scout.getNext())
return l