Why is string comparison failing in my code?

Question

I have an array in containing numbers that represent cable sizes (1, 1.5, 2.5, etc), stored as strings.

In my program, the array is loaded into a spinner, which is working fine. However, when the item is selected and stored in a variable, I want to check what string was selected, and set another numerical variable to 2.5 so I can do a calculation later in the program.

I tried the following:

if (conductorSize = "1" ) {conCsa = 1;}
else if (conductorSize = "1.5") {conCsa = 1.5;}

conductorSize being the variable holding the selected string, and conCsa being the variable set to a numerical variable for calculation.

The compiler says that I cannot convert a string to boolean. What's happening?

f20k · Accepted Answer · 2011-02-10 17:57:51Z

12

If you are doing string comparisons, use .equals() Example taken from here:

String s = "something", t = "maybe something else";
if (s == t)      // Legal, but usually WRONG.
if (s.equals(t)) // RIGHT <<<<<<<<<<<<< Use this.
if (s > t)    // ILLEGAL
if (s.compareTo(t) > 0) // CORRECT>

answered Feb 10, 2011 at 17:57

f20k

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1 Comment

f20k Over a year ago

If you are satisfied, please accept the answer by clicking the checkmark to the side of the question. =)

dave.c · Accepted Answer · 2011-02-10 18:05:29Z

3

As Ed S. points out you are using the assignment operator. However since you are comparing a String you need to use the equals method.

if ("1".equals(conductorSize)) {conCsa = 1;}
else if ("1.5".equals(conductorSize)) {conCsa = 1.5;}

Alternatively, you could just create a new float from your String:

float conCsa;
try {
    conCsa = Float.parseFloat(conductorSize);
}catch(NumberFormatException e){
    conCsa = 0.0f; //set to a default value
}

edited Feb 10, 2011 at 18:05

answered Feb 10, 2011 at 18:00

dave.c

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1 Comment

Thomas Over a year ago

Or Double.parseDouble(conductorSize) if a double is required/preferred.

David Hedlund · Accepted Answer · 2011-02-10 18:04:15Z

0

It looks like what you're trying to do might better be expressed in this way:

conCsa = Double.parseDouble(conductorSize);

answered Feb 10, 2011 at 18:04

David Hedlund

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1 Comment

R. Martinho Fernandes Over a year ago

Dammit, my vote limit for the day is over. I wanna upvote this answer!

ryanm · Accepted Answer · 2011-02-10 18:07:17Z

0

In general you need to use the .equals() method. If performance is extremely important and you are comparing against string literals, take a look at String.intern(). It'll allow you to do super-fast == comparisons and avoid a full character-by-character scan as in .equals(). Performance would have to be really, really important though, to justify such a non-standard approach.

answered Feb 10, 2011 at 18:07

ryanm

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Comments

Dead Programmer · Accepted Answer · 2011-02-10 20:08:48Z

0

When you have cable sizes which are constants, you need to use Enums , which will help you in reducing no of if condition comparisons.

answered Feb 10, 2011 at 20:08

Dead Programmer

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