If statement with a variable and no expression [duplicate]

Question

I came across these if statements while watching a Java pong game tutorial video:

boolean upAccel, downAccel; double y, velY; public HumanPaddle() { upAccel = false; downAccel = false; } public void setUpAccel(boolean input) { upAccel = input; } public void setDownAccel(boolean input) { downAccel = input; } // moves the paddle public void move() { /* What does the 'if(upAccel){ }' expression do..? */ if(upAccel) { velY -= 1; } if(downAccel) { velY += 1; } y = y + velY; }

So I understand that the setUpAccel and setDownAccel methods accept a boolean input which can either be true or false. However, I experimented with the if statements - and changed if(upAccel) to if(upAccel = true). Java didn't see the expression as the same thing, so I realized that the two expressions were different!

My question is, what does the if(upAccel) expression test out?

if (x == true) is equivalent to if (x) when x is a boolean. — hnefatl
– hnefatl, Commented Apr 15, 2018 at 15:07
If statements evaluate a boolean expression. Boolean variables can be used as boolean expressions. — Andy Turner
– Andy Turner, Commented Apr 15, 2018 at 15:07
= is assignment. == is comparison. So if (upAccel = true)... is the equivalent of upAccel = true; if (upAccel)... — T.J. Crowder
– T.J. Crowder, Commented Apr 15, 2018 at 15:13

Roushan · Accepted Answer · 2018-04-15 15:14:33Z

/* What does the 'if(upAccel){ }' expression do..? */ if(upAccel) { velY -= 1; }

it will evaluate to true can be rewritten as

/* What does the 'if(upAccel){ }' expression do..? */ if(upAccel==true) { velY -= 1; }

amk · Accepted Answer · 2018-04-15 15:08:26Z

0

The statement (upAccel) checks if the condition is true then it continues to perform velY -=1. (upAccel) is the same as (upAccel == true). The same goes with downAccel.

answered Apr 15, 2018 at 15:08

amk

707 bronze badges

2 Comments

MattGotJava Over a year ago

My bad, I was using one equal sign - which is used to ASSIGN variables, not set them. Thanks for the clarification.

amk Over a year ago

You're welcome, good luck.

Collectives™ on Stack Overflow

If statement with a variable and no expression [duplicate]

2 Answers 2

Comments

2 Comments

Linked

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

2 Comments

Linked

Related