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Java Android faq interview algorithms collections

Collections in java. don’t forget



Complexity pdf

wiki – Computational complexity theory

O notation

pdf, pdf

Введение в анализ сложности алгоритмов (часть 1) (

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

is lg n

Often Ignored Stuff — Android Data Structures (


  • 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



  • 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.


  1. differences between ArrayList and LinkedList
  2. HashMap
  3. BinaryTree

Interfaces, Classess:



wait, notify, notifyAll, concurrent

syncronized, volatile


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


Sparse collections

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