s6.pdf We have covered that material; you should read the chapter to reinforce what we did in class.

This material is from s7.pdf and s8.pdf

for(intit; test; between)
{
    BLOCK
}

for(Type item: collection)     for item in collection:
{                                  BLOCK
    BLOCK
}

if(predicate)                  if predicate:
{                                  BLOCK
    BLOCK
}

if(predicate)                   if predicate:
{                                   TRUEBLOCK
    TRIUEBLOCK                  else:
}                                   FALSEBLOCK
else
{
    FALSEBLOCK
}

if(predicate)                   if predicate:
{                                   TRUEBLOCK
    TRIUEBLOCK                  elif predicate2:
}                                   TRUE2BLOCK
else if(predicate2)             else:
{                                   DEFAULT BLOCK
    TRUE2BLOCK
}
else
{
    FALSEBLOCK
}

Time to switch

This is the switch-case statement.

public class StandOld
{
    public String fruit(char c)
    {
        String out = "";
        switch(c)  //chars, integer types, Strings, enums
        {
            case 'a': case 'A': 
                out = "apple";
                break;   //each case MUST end with a break.
            case 'b': case 'B':
                out = "blueberry";
                break;
            case 'c': case 'C':
                out = "cherry";
                break;
            case 'd': case 'e': 
                out = "kumquat";
                break;
            default:
                out = "No fruit with this letter";
        }
        return out;
    }
}

Ternary Operator

predicate? ifTrue: ifFalse

public class Foo
{
    public double f(double x)
    {
        return x < 0? -x:x;
    }
}

Python's

def f(x):
    return -x if x < 0 else x

Big Integer

This class gives Java a Python-like arbitrary-precision integer type. You will notice some important differences with Python, most of which are fairly cosmetic.

Recursion

Here is a little recursive factorial action.

import java.math.BigInteger;
public class Fact
{
    public static BigInteger factorial(int n)
    {
        if(n < 0)
        {
            throw new IllegalArgumentException();
        }
        if(n == 1 || n == 0)
        {
            return BigInteger.ONE;
        }
        return BigInteger.valueOf(n).multiply(factorial(n-1));
    }
    public static void main(String[] args)
    {
        System.out.println(factorial(1000));
        System.out.println(factorial(3));
        //System.out.println(factorial(-3));
        
        System.out.println(wabbit(2,3,4,5,6));
    }

}

while and do while

while(predicate)              while predicate:
{                                BLOCK
    BLOCK
}

do                      the NAG loop
{
    BLOCK
}while(predicate);

Starguments

import java.math.BigInteger;
public class Fact
{
    public static BigInteger factorial(int n)
    {
        if(n < 0)
        {
            throw new IllegalArgumentException();
        }
        if(n == 1 || n == 0)
        {
            return BigInteger.ONE;
        }
        return BigInteger.valueOf(n).multiply(factorial(n-1));
    }
    //stargument must be last argument
    //no keyword args in Java but you
    //do have method name overloading.
    public static int wabbit(int... factors)
    {
        int out = 1;
        for(int f: factors)  //java thinks factors is an array.
        {
            out *= f;
        }
        return out;
    }
    public static void main(String[] args)
    {
        System.out.println(factorial(1000));
        System.out.println(factorial(3));
        //System.out.println(factorial(-3));
        
        System.out.println(wabbit(2,3,4,5,6));
    }

}