// ------- IMPORTS ---------------------
import java.util.LinkedList;
import java.util.HashMap;

// ------- CLASSES AND INTERFACES ------
class A extends B implements I {
  ...
}

interface I {
  ...
}

// ---------- STRINGS -------------------
"kathi".length();
"kathi".equals("gompei");
  
// ---------- LISTS --------------------
LinkedList<String> myList;

// add item to the end of a list, returns void
myList.add("hi");

// add item to the beginning of a list, returns void
myList.addFirst("hi");

// check whether item is in a list, returns boolean
boolean b = myList.contains("hi");

// get item from a specific position in a list, first position is 0
String s = myList.get(3);

// get the length of the list
int length = myList.size();

// ---------- HASHMAPS ------------------
HashMap<String,Integer> myHM;

// put item into a hashmap, returns previous value or null
String prevVal = myHM.put("kathi", 130);

// get item from hashmap, returns null if no value for key
String value = myHM.get("kathi");

// --------- FOR ------------------------
for (TYPE VAR : LIST) {
  ...
}
  
for (VAR = INIT ; WHEN-TO-STOP ; UPDATE-VAR) {
  ...
}
  
// --------- IF --------------------------
if (TEST) {
  ...
} else { ... } 
    
// ------- BOOLEAN OPERATORS --------------
b1 && b1   // and
b1 || b2   // or
!b1        // not
  
// ------- NULL ----------------------------
Assign to a variable if need a way to say "no information"