File -> Settings -> Keymap you can do select Eclipse keymap from drop down menu

Ctrl+Shift+A (Help | Find Action on the main menu) and start typing the name of the action. Choose the desired action from the suggestion list.

Ctrl+Click (on Windows) or Cmd+Click (on MacOS) a tab in the editor to navigate to any part of the file path. Select the necessary element in the drop-down, and the corresponding file path opens in an external browser (e.g., in the Explorer, if your OS is Windows).

 

Find - Rename

Ctrl+F find

Refactor | Rename: Shift+F6  ( +F6)

Find and replace: CTRL + R

Go to variable declaration: CTRL + B

Ctrl+Shift+I (View | Quick Definition)

Ctrl+Alt+F7  (Edit | Find | Show Usages in the main menu)

Ctrl+Shift+F find in project

Ctrl+Shift+F7 (Edit | Find | Highlight Usages in File) to quickly highlight usages of some variable in the current file.
Use F3 and Shift+F3 keys to navigate through highlighted usages.
Press Escape to remove highlighting.

Ctrl+W (extend selection) in the editor selects the word at the caret and then selects expanding areas of the source code. For example, it may select a method name, then the expression that calls this method, then the whole statement, then the containing block, etc. You can also select the word at the caret and the expanding areas of the source code by double-clicking the target areas in the editor.

To search through the classes, files, tool windows, actions, settings, and symbols of your project by double pressing the Shift key

Ctrl+P (View | Parameter Info) e.g. localURL = new URL(localUrlString); select localUrlString and press Ctrl + P

Show html documentation tooltips:  CTRL + Q

 

Edit

Comment uncomment single line: CTRL + /

Comment uncomment selected text: CTRL + SHIFT + /

Code completion (Ctrl+Space)

Alt key and mouse pointer dragging for column selection

If nothing is selected in the editor, and you press Ctrl+C, then the whole line at caret is copied to the clipboard.

Ctrl + Delete  delete word from caret to end.

Ctrl + Backspace delete word from caret to start.

Duplicate line: CTRL + D

To compare two directories,or  jar files, select one or both of them in the Project view and press Ctrl+D.

Editor Delete Line: CTRL + Y

Move line UP, DOWN. Select a code fragment and press Ctrl+Shift+Up or Ctrl+Shift+Down.

To open any class or file in the editor at the desired line, press Ctrl+Shift+N (Navigate | File), start typing the name, and choose the one from the suggestion list. Then type the colon (:) and a line number

Ctrl+Shift+Enter to complete a current statement such as if, do-while, try-catch, return (or a method call)

Alt+Enter to invoke a quick fix or intention action, press the right arrow key to reveal the list of additional options.

To quickly review your recent changes to the project: Alt+Shift+C

Code Completion, you can accept the currently highlighted selection in the popup list with the period character (.), comma (,), semicolon (;), space and other characters.

Quickly move between methods in the editor:  Alt+Up and Alt+Down

Ctrl+Shift+J shortcut joins two lines into one and removes unnecessary space to match your code style

Ctrl+Shift+V to choose and insert recent clipboard contents into the text

Inheritance hierarchy for a selected class: Ctrl+H

Right-clicking on a breakpoint marker  you can quickly enable/disable the breakpoint or adjust its properties.

Evaluate the value of any expression while debugging the program, select its text in the editor (you may press a Ctrl+W a few times to efficiently perform this operation) and press Alt+F8.

Quickly evaluate the value of any expression while debugging the program, hold Alt and click this expression to see its value and calculate it, call a method, etc.

You can use the Extract Variable refactoring even on incomplete statements. Just select the necessary block in the editor and press Ctrl+Alt+V.

To open any particular method or field in editor: Ctrl+Alt+Shift+N

Add unimplemented methods: CTRL + I

Override methods: CTRL + O

Format code: CTRL + ALT + L

Show project: ALT + 1

Show logcat: ALT + 6

Hide project - logcat: SHIFT + ESC

Build: CTRL + F9

Build and Run: CTRL + F10

Alt+Shift+F10  access the Run/Debug dropdown on the main toolbar

Collapse all: CTRL + SHIFT + NumPad +

Expand all: CTRL + SHIFT + NumPad -

R.string to string Android source code
R.array to string [] Android source code

String s = getResources().getString(R.string.my_string); // Hello world!!
String[] arrayOfStrings = getResources().getStringArray(R.array.my_array); // one, two

<xml version="1.0" encoding="utf-8">
<resources>
    <string-array name="my_array">
        <item>one</item>
        <item>two</item>
    </string-array>
<string name="my_string">Hello world!!</string>
</resources>

int occupy 4 bytes (32 bits) in memory

int in Java example of using Integer and Array of Integer and Iteger to String

        // get max end min values of int in Java example 4 bytes (32 bits) PC architecture
	System.out.println(Integer.MAX_VALUE); // 2147483647
	System.out.println(Integer.MIN_VALUE); // -2147483648


// members variable
private int mProgress = 10;

//integer to string java
int myInteger = 8;
String myString = Integer.toString(myInteger);

// a final variable can only be initialized once
static final int NUM_PARTICLES = 15;

 for (int i = 0; i < NUM_PARTICLES ; i++) { 
// do something
}

// int as return value of function
public int getCount() {
return 5;
}

// int as a parametr of function
public float getFloatFromInt(int i) {
float fRet = (float) i;
 return fRet;
}

//array of int
int[] anArray;              // declares an array of integers
          anArray = new int[2];      // allocates memory for 2 integers
          anArray[0] = 100; // initialize first element
          anArray[1] = 200; // initialize second element

for (int i = 0; i < anArray.length; i++) {
// print out values from anArray
System.out.println("Index: " + i);
System.out.println("Value: " + anArray[i]); 
}

Link to tutorial

ArrayList Sublist of ArrayList Join two ArrayList Compare ArrayList Initialize ArrayList Loop ArrayList Sort ArrayList Array to ArrayList ArrayList to Array Synchronize ArrayList Serialize ArrayList LinkedList Loop LinkedList Vector ArrayList vs Vector ArrayList vs LinkedList HashMap Loop HashMap Synchronize HashMap Sort HashMap Serialize HashMap ArrayList vs HashMap TreeMap LinkedHashMap HashSet TreeSet LinkedHashSet ArrayList Methods