Why does 0 integer value behaves as false in if statement in groovy?
up vote
1
down vote
favorite
I wrote this part of code.
Integer value = 0
if(value)
{
print "true"
}
else
{
print "false"
}
And the output of code is false.
Can someone explain me why does Integer 0 value behaves as false in this if statement when it is not null and it exists?
if-statement groovy
asked Nov 20 at 13:26
Jakov Kusić
622312
add a comment |
up vote
1
down vote
favorite
I wrote this part of code.
Integer value = 0
if(value)
{
print "true"
}
else
{
print "false"
}
And the output of code is false.
Can someone explain me why does Integer 0 value behaves as false in this if statement when it is not null and it exists?
if-statement groovy
asked Nov 20 at 13:26
Jakov Kusić
622312
add a comment |
up vote
1
down vote
favorite
up vote
1
down vote
favorite
I wrote this part of code.
Integer value = 0
if(value)
{
print "true"
}
else
{
print "false"
}
And the output of code is false.
Can someone explain me why does Integer 0 value behaves as false in this if statement when it is not null and it exists?
if-statement groovy
asked Nov 20 at 13:26
Jakov Kusić
622312
I wrote this part of code.
Integer value = 0
if(value)
{
print "true"
}
else
{
print "false"
}
And the output of code is false.
Can someone explain me why does Integer 0 value behaves as false in this if statement when it is not null and it exists?
if-statement groovy
if-statement groovy
asked Nov 20 at 13:26
Jakov Kusić
622312
asked Nov 20 at 13:26
Jakov Kusić
622312
asked Nov 20 at 13:26
Jakov Kusić
622312
asked Nov 20 at 13:26
Jakov Kusić
622312
asked Nov 20 at 13:26
Jakov Kusić
622312
622312
add a comment |
add a comment |
2 Answers
2
active
oldest
votes
up vote
4
down vote
accepted
When Groovy sees a variable in the context where a boolean value is expected, it invokes DefaultGroovyMethods.asBoolean(object) method to coerce given value to its boolean representation. For numbers following code gets executed:
/**
* Coerce a number to a boolean value.
* A number is coerced to false if its double value is equal to 0, and to true otherwise,
* and to true otherwise.
*
* @param number the number
* @return the boolean value
* @since 1.7.0
*/
public static boolean asBoolean(Number number) {
return number.doubleValue() != 0;
}
Source: src/main/org/codehaus/groovy/runtime/DefaultGroovyMethods.java
That is why Groovy coerce 0 to false and any non-zero number to true.
There are other coercions that Groovy mades for you, e.g. empty list coerces to false, empty string coerces to false etc. I have written an article about some of them, you might find it useful.
answered Nov 20 at 13:31
Szymon Stepniak
16.5k83062
add a comment |
up vote
5
down vote
It's part of the "Groovy Truth"
5.7. Numbers
Non-zero numbers are true.
assert 1
assert 3.5
assert !0
answered Nov 20 at 13:31
cfrick
18k13452
add a comment |
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2 Answers
2
active
oldest
votes
2 Answers
2
active
oldest
votes
active
oldest
votes
active
oldest
votes
up vote
4
down vote
accepted
When Groovy sees a variable in the context where a boolean value is expected, it invokes DefaultGroovyMethods.asBoolean(object) method to coerce given value to its boolean representation. For numbers following code gets executed:
/**
* Coerce a number to a boolean value.
* A number is coerced to false if its double value is equal to 0, and to true otherwise,
* and to true otherwise.
*
* @param number the number
* @return the boolean value
* @since 1.7.0
*/
public static boolean asBoolean(Number number) {
return number.doubleValue() != 0;
}
Source: src/main/org/codehaus/groovy/runtime/DefaultGroovyMethods.java
That is why Groovy coerce 0 to false and any non-zero number to true.
There are other coercions that Groovy mades for you, e.g. empty list coerces to false, empty string coerces to false etc. I have written an article about some of them, you might find it useful.
answered Nov 20 at 13:31
Szymon Stepniak
16.5k83062
add a comment |
up vote
4
down vote
accepted
When Groovy sees a variable in the context where a boolean value is expected, it invokes DefaultGroovyMethods.asBoolean(object) method to coerce given value to its boolean representation. For numbers following code gets executed:
/**
* Coerce a number to a boolean value.
* A number is coerced to false if its double value is equal to 0, and to true otherwise,
* and to true otherwise.
*
* @param number the number
* @return the boolean value
* @since 1.7.0
*/
public static boolean asBoolean(Number number) {
return number.doubleValue() != 0;
}
Source: src/main/org/codehaus/groovy/runtime/DefaultGroovyMethods.java
That is why Groovy coerce 0 to false and any non-zero number to true.
There are other coercions that Groovy mades for you, e.g. empty list coerces to false, empty string coerces to false etc. I have written an article about some of them, you might find it useful.
answered Nov 20 at 13:31
Szymon Stepniak
16.5k83062
add a comment |
up vote
4
down vote
accepted
up vote
4
down vote
accepted
When Groovy sees a variable in the context where a boolean value is expected, it invokes DefaultGroovyMethods.asBoolean(object) method to coerce given value to its boolean representation. For numbers following code gets executed:
/**
* Coerce a number to a boolean value.
* A number is coerced to false if its double value is equal to 0, and to true otherwise,
* and to true otherwise.
*
* @param number the number
* @return the boolean value
* @since 1.7.0
*/
public static boolean asBoolean(Number number) {
return number.doubleValue() != 0;
}
Source: src/main/org/codehaus/groovy/runtime/DefaultGroovyMethods.java
That is why Groovy coerce 0 to false and any non-zero number to true.
There are other coercions that Groovy mades for you, e.g. empty list coerces to false, empty string coerces to false etc. I have written an article about some of them, you might find it useful.
answered Nov 20 at 13:31
Szymon Stepniak
16.5k83062
When Groovy sees a variable in the context where a boolean value is expected, it invokes DefaultGroovyMethods.asBoolean(object) method to coerce given value to its boolean representation. For numbers following code gets executed:
/**
* Coerce a number to a boolean value.
* A number is coerced to false if its double value is equal to 0, and to true otherwise,
* and to true otherwise.
*
* @param number the number
* @return the boolean value
* @since 1.7.0
*/
public static boolean asBoolean(Number number) {
return number.doubleValue() != 0;
}
Source: src/main/org/codehaus/groovy/runtime/DefaultGroovyMethods.java
That is why Groovy coerce 0 to false and any non-zero number to true.
There are other coercions that Groovy mades for you, e.g. empty list coerces to false, empty string coerces to false etc. I have written an article about some of them, you might find it useful.
answered Nov 20 at 13:31
Szymon Stepniak
16.5k83062
answered Nov 20 at 13:31
Szymon Stepniak
16.5k83062
answered Nov 20 at 13:31
Szymon Stepniak
16.5k83062
answered Nov 20 at 13:31
Szymon Stepniak
16.5k83062
16.5k83062
add a comment |
add a comment |
up vote
5
down vote
It's part of the "Groovy Truth"
5.7. Numbers
Non-zero numbers are true.
assert 1
assert 3.5
assert !0
answered Nov 20 at 13:31
cfrick
18k13452
add a comment |
up vote
5
down vote
It's part of the "Groovy Truth"
5.7. Numbers
Non-zero numbers are true.
assert 1
assert 3.5
assert !0
answered Nov 20 at 13:31
cfrick
18k13452
add a comment |
up vote
5
down vote
up vote
5
down vote
It's part of the "Groovy Truth"
5.7. Numbers
Non-zero numbers are true.
assert 1
assert 3.5
assert !0
answered Nov 20 at 13:31
cfrick
18k13452
It's part of the "Groovy Truth"
5.7. Numbers
Non-zero numbers are true.
assert 1
assert 3.5
assert !0
answered Nov 20 at 13:31
cfrick
18k13452
answered Nov 20 at 13:31
cfrick
18k13452
answered Nov 20 at 13:31
cfrick
18k13452
answered Nov 20 at 13:31
cfrick
18k13452
18k13452
add a comment |
add a comment |
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