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Java Android faq interview algorithms collections

Collections in java. don’t forget

https://habrahabr.ru/post/162017/

https://habr.com/post/156361/

https://habrahabr.ru/post/237043/

364d7e41907e453b8e60128cdac459dc

2016-12-04_00-29-25


Complexity pdf

wiki – Computational complexity theory

O notation

pdf, pdf

Введение в анализ сложности алгоритмов (часть 1) (https://habr.com/post/196560/)

int a = 1;
while (a < n) {
    a = a * 2;
}

is lg n


https://auth0.com/blog/best-practices-in-android-development/

Often Ignored Stuff — Android Data Structures (https://medium.com/@ankitsharma6466/often-ignored-stuff-android-data-structures-ec2efff847ea)

Tips:

  • JPA, Hibernate pdf
  • java opensource on github pdf
  • collections (jdk, guava, apache etc) pdf
  • java stream api pdf dzone
  • studing java pdf
  • links pdf
  • inputstream into string pdf
  • map, substring in string pdf
  • json pdf

Android


Android

  • fragment, inner fragments, childFragmentManager, what to use instead of fragments
  • save state of app, onSaveInstanceStatesetRetainInstance(true)onRetainNonConfigurationInstance
  • inner classes in java, types of them;
  • types of references in java
  • hot to determine complexity of quicksort

Object methods

public native int hashCode();
public boolean equals(Object obj) {
  return (this == obj);
}
protected native Object clone() throws CloneNotSupportedException;
public String toString() {
  return getClass().getName() + "@" + Integer.toHexString(hashCode());
}
public final native void notify();
public final native void notifyAll();
public final native void wait(long timeout) throws InterruptedException;
protected void finalize() throws Throwable { }

ob1.Equals(ob2) --> ob1.hashcode == ob2.hashcode

Map is not a collection.

Questions:

  1. differences between ArrayList and LinkedList
    https://habrahabr.ru/post/162017/
    https://habrahabr.ru/post/159557/
    https://habrahabr.ru/post/128269/
    https://habrahabr.ru/post/127864/
  2. HashMap
  3. BinaryTree
    BalancedTree

Interfaces, Classess:

java-collections_api-collection

Multithreading

wait, notify, notifyAll, concurrent

syncronized, volatile

Android

There are 4 main components: activity, service, broadcastreceiver, ContentProvider

BroadcastReceiver can be registered in manifest or in code.

Service lifecycle:

Restart of service:

Service in UI and service in another thread

Activity lifecycle:

if a view has ID then

Activity.OnCreate(Bundle)


Sparse collections

HashMap Array class
<Integer, Object> SparseArray
<Integer, Boolean> SparseBooleanArray
<Integer, Integer> SparseIntArray
<Integer, Long> SparseLongArray
<Long, Object> LongSparseArray
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