CodeHS

Java Karel's Built in Commands

move();		turnLeft();
putBall();		takeBall();

Methods

Writing a method is like teaching karel a new word.

Naming Methods: You can name your methods whatever you want, but you can't have spaces in the method name.

Remember that each open bracket { must match with a close bracket }

private void turnRight()
{
    turnLeft();
    turnLeft();
    turnLeft();
}

private void turnAround()
{
    turnLeft();
    turnLeft();
}

private void yourMethodName()
{
  // Code that will run when you make a call to
  // this method.
}

Conditional Statements

Remember that each open bracket { must match with a close bracket }

if (condition) 
{
  //code that will run if the condition is true
}

if (condition) 
{
  //code that will run if the condition is true
}
else
{
  //code that will run if condition is not true
}

Example of if statements

if(frontIsClear())
{
  move();
}

if(ballsPresent())
{
  takeBall();
}
else
{
  move();
}

Karel Conditions

Don't forget the () at the end

frontIsClear()
leftIsClear()
rightIsClear()

facingNorth()
facingSouth()
facingEast()
facingWest()

ballsPresent()

frontIsBlocked()
leftIsBlocked()
rightIsBlocked()

notFacingNorth()
notFacingSouth()
notFacingEast()
notFacingWest()

noBallsPresent()

Loops

Remember that each open bracket { must match with a close bracket }

While Loops

while (CONDITION)
{
  // Code that will run while the CONDITION is true.
  // Once the CONDITION is no longer true,
  // it will stop.
}

Example of while loops

/* This moves Karel to a wall */
while(frontIsClear())
{
    move();
}

For Loops

for (int i=0; i < COUNT; i++)
{
  // Code that will run 'COUNT' times
}

Example of for loops

/* This puts down 10 balls */
for(int i = 0; i < 10; i++)
{
    putBall();
}

You can have multiple statements or function calls in a for loop.

/* This puts down five balls and
   moves after each one */
for(int i = 0; i < 5; i++)
{
    putBall();
    move();
}

Use for-loops when you want to repeat something a fixed number of times.

Use while-loops when you want to repeat something as long as a condition is true.

Comments

/* A multi-line comment describes your code
 * to someone who is reading it. */

// Use single line comments to clarify code.

/**
 *
 * A Javadoc comment
 * is used to describe how a
 * method or class works.
 *
 * It has two *'s on the first line.
 */