java-cheatsheet.md

Operation	Code
New List	List<Integer> x = new ArrayList<Integer>();
Copy List	List<Integer> x = new ArrayList<Integer>(y);
Add an element to the List	x.add(element)
Get an elemenet from the List	x.get(index)
Clear the list	x.clear()
New HashMap	HashMap<Integer, String> x = new HashMap<Integer, String>();
Add element to the map	x.put(key, value)
Get an element from the map	x.get(key)
Declare a class	public class Ideone extends Main implements Runnable { ... }
Declare a function	public static List<String> weave(String a1, String a2)
Append to a StringBuilder	StringBuilder b = new StringBuilder();b.append(...);
Prepend to a StringBuilder	b.insert(0, "text");
Get a substring from a string	str.substring(i, j)