Collections
Duplicates
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Null values
|
description
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Array list
|
Yes,
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yes
|
1)Reterival Purpose
2)DataStruture is Resizable or growable array
3)Insertion order preserved,
4)duplicates Objects allowed
5)null insertion possible
6)Hetrogenious Objects allowed
7)Implemented the following Marker interfaces
1)Randam access interface
2)serilizable interface
3)clonnable Interface
|
Linked list
|
yes
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yes
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1)Insertion& deletion in middle purpose using
2)DataStruture is DoublyLinkedList
3)Insertion order preserved,
4)duplicates Objects allowed
5)null insertion possible
6) Hetrogenious Objects allowed
6)Implemented the following Marker interfaces
1)serilizable interface
2)clonnable Interface
|
Vector(legacy)
|
yes
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yes
|
1)DataStruture is Resizable or growable array
2)Insertion order preserved,
3)duplicates Objects allowed
4)null insertion possible
5) Hetrogenious Objects allowed
6)Implemented the following Marker interfaces
1)Randam access interface
2)serilizable interface
3)clonnable Interface
|
Stack
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Child class of vector
|
Duplicates
|
Null values
|
Decription
| |
Hashset(1.2)
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no
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Only Once
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1)DataStruture is Hashtable
2)Insertion order not preserved,
Based on Hashcode of object the data will be stored(some random order)
3)duplicates not Objects allowed
If we trying to add duplicate values
It won’t through CTE(or)RTE,add()simply returns false
4)null insertion possible only once
If we trying to add duplicate null values
It won’t through CTE(or)RTE
5) Hetrogenious Objects allowed
6)Implemented the following Marker interfaces
1)serilizable interface
2)clonnable Interface
7)search purpose useful
|
LinkedHashset
|
no
|
Only Once
|
similarly to above,But
1)Datastruture is LinkedList+hashTable
2)Insertion order preserved
3)linkedhasshset&linkedhashmap are best suitable for Cache memory
|
Tree set
Eg:
TreeSet ts=new TreeSet();
ts.add(null);
ts.add("r");
system.out.println(ts);
O/P:
NullPointerException
raised
|
no
|
no
|
1)DataStruture is Balance Tree
2)Insertion order not preserved,
All the elements are stored in some sorting order
3)duplicates Objects not allowed
If we trying to add duplicate values
It won’t through CTE(or)RTE, it ignores the duplicate value
4)null insertion not possible
If we trying to add null values
It throws “NullPointerException”
5) Hetrogenious Objects not allowed
If we trying to add other values it throws “ClassCastException”
6)Implemented the following Marker interfaces 1)serilizable interface
2)clonnable Interface
7)Only Homogenious element allowed
8)search purpose useful
|
For Key: “keyvalue” and “keynull value” the latest will remain, the past value will be gone
IOP:insertion order preserved IONP:Insertion Order not preserved
DA:Duplicates Allowed
DNA:Duplicates not allowed ,NPE :Null Pointer Exception CCE:Class Cast Exception
NIPOOFK: Null insertion is possible Only once for Key , DS:DataStruture
Dupicates
(key,value)
|
Null
(key,value)
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description
| |||||||||||
HashMap
(1.2)
1)(jvm uses equals() to identify duplicates keys)
2)Domianate Garbage collector
|
(no,yes)
|
(yes(only once),yes)
|
1)HashMap under lying DS is HashTable
2) Insertion order not preserved,
Based on Hashcode of object the data will be stored(some random order)
3)Hetrogenious and Homogenious objects are allowed for both key and values
| ||||||||||
LinkedHashmap
(1.4)
|
(no,yes)
|
(yes(only once),yes)
|
1) similarly to above,But Insertion order preserved
2) linkedhasshset&linkedhashmap are best suitable for Cache memory
| ||||||||||
TreeMap(1.2)
|
(no,yes)
|
(no,yes)
|
1)TreeMap under lying DS -RED-BLACK SORT
2) Insertion order not preserved,
All the elements are stored in some sorting order
3) Hetrogenious objects are not allowed for keys and Hetrogenious objects are allowed for values
For an empty TreeMap ,as first element “null” as key can be inserted then after no other (key,value)pair inserted
Eg:=
1)
TreeMap tm=new TreeMap();
tm.put(null,"v3");
System.out.println(tm);
O/P:[null,v3]
2) TreeMap tm=new TreeMap();
tm.put(null,"v3");
tm.put(1, "key");
System.out.println(tm);
O/P: NullPointerException raised
| ||||||||||
LinkedHashMap
|
(no,yes)
|
(no,yes)
|
Similar to HashMap ,But insertion order is reserved
| ||||||||||
IdentityhashMap
1)(jvm uses “==” to identify duplicates keys)
|
(no,yes)
|
(yes(only once),yes)
|
Similar to HashMap
| ||||||||||
WeakHashMap
|
(no,yes)
|
(yes(only once),yes)
|
Similar to HashMap
|
1)LinkedHashMap = HashMap
(Insertion order is preserved) | (Insertion order is not preserved)
2)IdentityHashMap =HashMap
(JVM uses”==” operator to |(JVM uses equals() to isentify Duplicate keys)
Identify Duplicate keys)
3)WeakHashMap =HashMap
HashMap object is not eligiable for garabage collection.if it associated with hashMap even through,even through it doesnot have any external reference(i.e HashMap Dominates Garbage collector)
In WeakHashMap an object is not havaing any external reference then it is alwayseligiable for for garabage collectioneven through it associated with weakHashMap.(i.e., Garbage collector dominate the weakHashMap).
Ruffly Remember
1)Any “List” Insertion Order Preserved,Duplicates allowed,null value allowed
2)Any “Set” Insertion Order not preserved,Duplicated not allowed,null not allowed(varies some time)
3)Any “Tree” insertion Order not preserved,duplicates not allowed,Sorted order of elements(Default Ascending order)
4)Map(key, value): Key Unique,value may be duplicate
====================================================================
Type of Cursors
1)Enumeration(i)(legacy) --Forward
1) Public Boolean hasMoreElements()
2)Public Object nextElement()
2)Iterator(i)—Forward,Remove
1) Public Boolean hasNext()
2)Public Object next()
3) Public void remove()
3)ListIterator(i)—Forward,Backward,Remove,Replace
1) Public Boolean hasNext()
2) Public Boolean hasPrevious()
3)Public Object next()
4) Public Object Previous ()
3) Public void remove()
======================================================================
Language fundamentals
1)Identifier
2)keywords
3)Datatypes
4)Literals
5)Arrays
6)Types of variables
7)var-args methods
8)java coding Standards
9)Commmand linearguments and the main()
Identifier: (Name of theVaribles,methods,classesand labels)
Consists of a sequence of characters (a toz) to Digits(0-9)or Currenbcy symbols($)orConnecting puncuvations(_)
Reserved Words(8+11+6+11+6+4+1+3+1)
DataTypes(8):bytet,short,int,long,float,double,Boolean,char
Flow Control(11):if,else,switch,case,default,for,do,while,break,continue,return
Exception Handling(6):try,catch,finally,throw,throws,assert
Modifier:Access specifiers(11) :(privateprotected,default,public)&(static,abstract,final,synchronized,native,transient,volatile,strictfp)
Class Relateed Keywords(6):interface,class,package,import,extends,implementas
Object related keyword(4):new,instanceof,super
Void return type key word(1)
Reserved literals(3):true,false(value for boolean dataype),null(value for object reference)
MSB(most significant bit )
0 ->+ive
1 ->-ve
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