Java basics Cheat Sheet (DRAFT) by [deleted]

javac Program.java //compile
java program,Program
javac -Xlint:unchecked Program.java //check warnings

package program;
public class Program{
  public static void main(String[] args){ ... }

import java.util.*;
  java.util.ArrayList;
  java.util.Scanner;
import java.io.*;
import java.math.*;

public - pristupne odvsadial
protected - v ramci package, triedy a podtried
private - v ramci triedy
(no modifier) - v ramci package

abstract - neimplementovana metoda / trieda
final
  var - nemenna
  method - neda sa Override
  class - neda sa dedit
static - methods sa tykaju celej triedy nie konkr. instancie

extends
//vytvaranie podtried
class Shape { ... }
class Circle extends Shape { ... }
instanceof //boolean
//je instanciou triedy
if (x isinstanceof Shape){ ... }
@Override
//pred prekryvanou metodou
super
//volanie metody z nadtriedy v podtriede
super.method();

//premenna this je referencia na konkr. objekt, na kt. bola metoda zavolana
//napr.
class Contact {
   private String email;
   public void setName(String name) {  
       this.name = name; }
}

//KONZOLA
System.out.print(String); / System.out.println(String);
System.out.format("%x",var);
//BUFFERED READER
BufferedReader input = new BufferedReader(new 
   InputStreamReader(System.in));
String line = input.readLine()  //null ak uz koniec
//SCANNER
Scanner input = new Scanner(System.in);
input.hasNext(); //boolean
input.next(); //dalsi znak
input.nextInt(); //convert. na int
//FILE input - BufferedReader/Scanner
// System.in -> "file.txt"
input.close()
//FILE output - PrintStream
PrintStream output = new PrintStream("file.txt");
output.print/println/format(String);
output.close();

ArrayList
list.size() // # prvkov
list.get(i) / ,add(x) / .set(i,x);
ArrayList<type> newList = new ArrayList<type>(list)
   //skopirovanie obsahu do novej instancie
String
text.length() //dlzka
modText = text.substring(beg_i,end_i);
   //copy string od do
text = String.format("%x",var); //format ako printf
char x = text.charAt(i);

class Node <T> {
  private T data;
  public Node(T data){
    this.data = data; }
  public T getData() {
    return data; }