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(((急!!!!)))JAVA Link List
有誰能幫我解釋(註解) 以下這段藍色程式的每一行!!!!!!!!
拜託~~我很急....
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class ListNode
{
Object data;
ListNode nextNode;
ListNode( Object object )
{
this( object, null );
}
ListNode( Object object, ListNode node )
{
data = object;
nextNode = node;
}
Object getObject()
{
return data;
}
ListNode getNext()
{
return nextNode;
}
}
public class List
{
private ListNode firstNode;
private ListNode lastNode;
private ListNode Node;
private String name;
public List()
{
this( "list" );
}
public List( String listName )
{
name = listName;
firstNode = lastNode = null;
}
// 從任意位置插入
public boolean insertAtAnywhere( Object insertItem, int index )
{
if ( isEmpty() || index < 0 )
return false;
else if ( index == 1 ) //如果輸入的位置為1
{
// 從第一個插入
insertAtFront( insertItem );
return true;
}
ListNode current = firstNode;
int count = 1;
while(current != null )
{
if(count+1 == index)
{
Node = current.nextNode ;
current.nextNode = new ListNode( insertItem );
current.nextNode.nextNode = Node;
}
current=current.nextNode;
count++;
}
return false;
}
// 從任意位置刪除
public Object removeFromAnywhere( int index ) throws EmptyListException
{
if ( isEmpty() || index < 0 )
return false;
else if ( index == 1 ) //如果輸入要刪除的位置為1
{
// 從第一個刪除
removeFromFront();
return true;
}
Object removedItem = lastNode.data;
ListNode current = firstNode;
int count = 1;
while(current != null )
{
if(count+1 == index)
{
current.nextNode = current.nextNode.nextNode ;
}
current = current.nextNode;
count++;
}
return removedItem;
}
public boolean isEmpty()
{
return firstNode == null;
}
public void print()
{
if ( isEmpty() )
{
System.out.printf( "Empty %s\n", name );
return;
}
System.out.printf( "The %s is: ", name );
ListNode current = firstNode; while ( current != null )
{
System.out.printf( "%s ", current.data );
current = current.nextNode;
}
System.out.println( "\n" );
} }
2 Answers
- ?Lv 710 years agoFavorite Answer
public boolean insertAtAnywhere(Object insertItem, int index) { // if the list is empty or invalid index (<0) // insertion failed and return false if ( isEmpty() || index < 0 ) return false; else if (index == 1) { // index=1, insert at front and return true for insertion success insertAtFront( insertItem ); return true; } // if none of the above conditions are true, traverse forward using a // while loop and insert at indexed position ListNode current = firstNode; // set the current pointer at first node int count = 1; // the while loop ends when the node is null, which should be next // to last node while (current != null ) { if (count+1 == index) { // in the beginnning, the list is // ... -> current -> inNode -> ... // the the next to current node is the index requested, do // 1. use a temp node (inNode) hold the next to current node inNode = current.nextNode ; // 2. set the next node of current one as the inserted node current.nextNode = new ListNode( insertItem ); // 3. set the next to the new-inserted node as the temp node current.nextNode.nextNode = inNode; // in the end, the list is altered as // ... -> current -> insertedNode -> inNode -> .... // since the insertion completes here, a return is missing // return true; } // if required index not reached, move forward to the next index current=current.nextNode; count++; } // the requested index is not reached or not found, insertion failed return false; } // end method insertAtAnywhere public Object removeFromAnywhere(int index) throws EmptyListException { // if the list is empty or invalid index (<0) // removal failed and return false if (isEmpty() || index < 0) // should return null instead of 'false' return false; else if (index == 1) { //如果輸入要刪除的位置為1 // 從第一個刪除 removeFromFront(); // should return the removedItem instead of 'true' return true; }
字數有限, 餘見意見欄
2011-05-23 12:14:35 補充：
// removedItem retrieves data being removed, but should not
// be the last node. Obviously this is copied from other methods
Object removedItem = lastNode.data;
2011-05-23 12:14:52 補充：
// if none of the above conditions are true, traverse forward using a
// while loop and remove at indexed position
ListNode current = firstNode;
int count = 1;
// the while loop ends when the node is null, which should be next
// to last node.
2011-05-23 12:15:25 補充：
while(current != null ) {
if(count+1 == index) {
// set the next to current node to the second next one
// before: .. -> current -> next1 -> next2 -> ...
// after: .. -> current -> next2 -> ... (next1 removed)
2011-05-23 12:15:33 補充：
// removeItem should hold the reference first
// removedItem = current.nextNode;
current.nextNode = current.nextNode.nextNode ;
}
current = current.nextNode;
count++;
}
2011-05-23 12:15:40 補充：
return removedItem;
} // end method removeFromAnywhere
