String replace() returns extra space in Java

up vote
16
down vote

favorite

Consider:

System.out.println(new String(new char[10]).replace("", "hello"));

has output:

hellohellohellohellohellohellohellohellohellohello

but:

System.out.println(new String(new char[10]).replace("", "hello"));

has output:

hello hello hello hello hello hello hello hello hello hello

Where are these extra spaces coming from?

edited Aug 20 at 10:15

Sun

13.1k31541

asked Aug 18 at 16:02

Ansh

964

You should loop through the string and print each character.
â€“Â copper.hat
Aug 18 at 22:56

1

@Ferrybig There was never a trailing space. The OP's original description was (presumably) incorrect. See for example ideone.com/492Cml.
â€“Â Radiodef
Aug 19 at 2:43

add a commentÂ |Â

up vote
16
down vote

favorite

Consider:

System.out.println(new String(new char[10]).replace("", "hello"));

has output:

hellohellohellohellohellohellohellohellohellohello

but:

System.out.println(new String(new char[10]).replace("", "hello"));

has output:

hello hello hello hello hello hello hello hello hello hello

Where are these extra spaces coming from?

edited Aug 20 at 10:15

Sun

13.1k31541

asked Aug 18 at 16:02

Ansh

964

You should loop through the string and print each character.
â€“Â copper.hat
Aug 18 at 22:56

1

@Ferrybig There was never a trailing space. The OP's original description was (presumably) incorrect. See for example ideone.com/492Cml.
â€“Â Radiodef
Aug 19 at 2:43

add a commentÂ |Â

up vote
16
down vote

favorite

Consider:

System.out.println(new String(new char[10]).replace("", "hello"));

has output:

hellohellohellohellohellohellohellohellohellohello

but:

System.out.println(new String(new char[10]).replace("", "hello"));

has output:

hello hello hello hello hello hello hello hello hello hello

Where are these extra spaces coming from?

edited Aug 20 at 10:15

Sun

13.1k31541

asked Aug 18 at 16:02

Ansh

964

Consider:

System.out.println(new String(new char[10]).replace("", "hello"));

has output:

hellohellohellohellohellohellohellohellohellohello

but:

System.out.println(new String(new char[10]).replace("", "hello"));

has output:

hello hello hello hello hello hello hello hello hello hello

Where are these extra spaces coming from?

edited Aug 20 at 10:15

Sun

13.1k31541

asked Aug 18 at 16:02

Ansh

964

edited Aug 20 at 10:15

Sun

13.1k31541

edited Aug 20 at 10:15

Sun

13.1k31541

edited Aug 20 at 10:15

Sun

13.1k31541

asked Aug 18 at 16:02

Ansh

964

asked Aug 18 at 16:02

Ansh

964

asked Aug 18 at 16:02

Ansh

964

You should loop through the string and print each character.
â€“Â copper.hat
Aug 18 at 22:56

1

@Ferrybig There was never a trailing space. The OP's original description was (presumably) incorrect. See for example ideone.com/492Cml.
â€“Â Radiodef
Aug 19 at 2:43

add a commentÂ |Â

You should loop through the string and print each character.
â€“Â copper.hat
Aug 18 at 22:56

1

@Ferrybig There was never a trailing space. The OP's original description was (presumably) incorrect. See for example ideone.com/492Cml.
â€“Â Radiodef
Aug 19 at 2:43

You should loop through the string and print each character.
â€“Â copper.hat
Aug 18 at 22:56

@Ferrybig There was never a trailing space. The OP's original description was (presumably) incorrect. See for example ideone.com/492Cml.
â€“Â Radiodef
Aug 19 at 2:43

add a commentÂ |Â

4 Answers
4

active

oldest

votes

up vote
14
down vote

It is not a space. It is how your IDE/console shows character which new char[10] is filled with by default.

You are not replacing with anything, so it stays in string. Instead with .replace("", "hello") you are replacing only empty string "". Important thing is that Java assumes that "" exists at:

start of the string,

end of string,

and between each of the characters

since we can get "abc" with:

"abc" = "" + "a" + "" + "b" + "" + "c" + ""`;
 //^ ^ ^ ^

Now .replace("", "hello") replaces each of those "" with "hello", so for string of length 10 it will place additional 11 hellos (not 10), without modifying , which will be shown at your output like spaces.

Maybe this will be easier to grasp:

System.out.println("aaa".replace("", "X"));

lets represent each "" with as |. We will get "|a|a|a|" (notice that there are 4 |)

so replacing "" with X will result in "XaXaXaX" (but in your case instead of a your console will print using character which will look like space)

edited Aug 18 at 17:17

answered Aug 18 at 16:16

Pshemo

91.1k14127178

add a commentÂ |Â

up vote
11
down vote

Short version

represents character NUL, it does not equals empty string "".

Long version

When you try to create a String with empty char[10],:
```
String input = new String(new char[10]);
```
this String will contains 10 NUL character:
```
|NUL|NUL|NUL|NUL|NUL|NUL|NUL|NUL|NUL|NUL|
```

When you call input.replace("", "hello"), the NUL value() will be replaced by hello:
```
|hello|hello|hello|hello|hello|hello|hello|hello|hello|hello|
```

When you call input.replace("", "hello"), the NUL value will not be replaced since it does not match empty string "":
```
|hello|NUL|hello|NUL|hello|NUL|hello|NUL|hello|NUL|hello|NUL|hello|NUL|hello|NUL|hello|NUL|hello|NUL|hello|
```

edited Aug 18 at 19:15

answered Aug 18 at 16:19

Sun

13.1k31541

add a commentÂ |Â

up vote
7
down vote

Explanation

You are using the method String#replace(CharSequence target, CharSequence replacement) (documentation).

If invoked with an empty target character sequence replace("", replacement) it will not replace the elements in the source, but insert the replacement before every character.

This is because "" matches the positions between the characters, not the characters themselves. So every position between will be replaced, i.e. replacement is inserted.

Example:

"abc".replace("", "d") // Results in "dadbdcd"

Your string contains only the default value of char at every position, it is

using the method thus results in:

hellohellohellohellohellohellohellohellohellohello

Display

Your console probably displayed the character as whitespace, while it's actually not a whitespace but .

If I try out your code in a different console, I get:

enter image description here

Confirming that the characters are indeed not spaces but something different (i.e. ).

edited Aug 18 at 16:21

answered Aug 18 at 16:15

Zabuza

10.6k52538

replace("", ...) inserts the replacement at the end of the string too. See e.g. ideone.com/492Cml.
â€“Â Radiodef
Aug 19 at 2:45

add a commentÂ |Â

up vote
3
down vote

char's default value is u0000 which can also be represented as . So your new char[10] contains 10 s.

In the first statement you clearly replace with "hello". But in the second statement you leave out the default value. Which your IDE output chooses to show as a space.

answered Aug 18 at 16:28

Roshana Pitigala

3,57162342

add a commentÂ |Â

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4 Answers
4

active

oldest

votes

4 Answers
4

active

oldest

votes

up vote
14
down vote

It is not a space. It is how your IDE/console shows character which new char[10] is filled with by default.

You are not replacing with anything, so it stays in string. Instead with .replace("", "hello") you are replacing only empty string "". Important thing is that Java assumes that "" exists at:

start of the string,

end of string,

and between each of the characters

since we can get "abc" with:

"abc" = "" + "a" + "" + "b" + "" + "c" + ""`;
 //^ ^ ^ ^

Maybe this will be easier to grasp:

System.out.println("aaa".replace("", "X"));

lets represent each "" with as |. We will get "|a|a|a|" (notice that there are 4 |)

so replacing "" with X will result in "XaXaXaX" (but in your case instead of a your console will print using character which will look like space)

edited Aug 18 at 17:17

answered Aug 18 at 16:16

Pshemo

91.1k14127178

add a commentÂ |Â

up vote
14
down vote

It is not a space. It is how your IDE/console shows character which new char[10] is filled with by default.

You are not replacing with anything, so it stays in string. Instead with .replace("", "hello") you are replacing only empty string "". Important thing is that Java assumes that "" exists at:

start of the string,

end of string,

and between each of the characters

since we can get "abc" with:

"abc" = "" + "a" + "" + "b" + "" + "c" + ""`;
 //^ ^ ^ ^

Maybe this will be easier to grasp:

System.out.println("aaa".replace("", "X"));

lets represent each "" with as |. We will get "|a|a|a|" (notice that there are 4 |)

so replacing "" with X will result in "XaXaXaX" (but in your case instead of a your console will print using character which will look like space)

edited Aug 18 at 17:17

answered Aug 18 at 16:16

Pshemo

91.1k14127178

add a commentÂ |Â

up vote
14
down vote

It is not a space. It is how your IDE/console shows character which new char[10] is filled with by default.

You are not replacing with anything, so it stays in string. Instead with .replace("", "hello") you are replacing only empty string "". Important thing is that Java assumes that "" exists at:

start of the string,

end of string,

and between each of the characters

since we can get "abc" with:

"abc" = "" + "a" + "" + "b" + "" + "c" + ""`;
 //^ ^ ^ ^

Maybe this will be easier to grasp:

System.out.println("aaa".replace("", "X"));

lets represent each "" with as |. We will get "|a|a|a|" (notice that there are 4 |)

so replacing "" with X will result in "XaXaXaX" (but in your case instead of a your console will print using character which will look like space)

edited Aug 18 at 17:17

answered Aug 18 at 16:16

Pshemo

91.1k14127178

It is not a space. It is how your IDE/console shows character which new char[10] is filled with by default.

You are not replacing with anything, so it stays in string. Instead with .replace("", "hello") you are replacing only empty string "". Important thing is that Java assumes that "" exists at:

start of the string,

end of string,

and between each of the characters

since we can get "abc" with:

"abc" = "" + "a" + "" + "b" + "" + "c" + ""`;
 //^ ^ ^ ^

Maybe this will be easier to grasp:

System.out.println("aaa".replace("", "X"));

lets represent each "" with as |. We will get "|a|a|a|" (notice that there are 4 |)

so replacing "" with X will result in "XaXaXaX" (but in your case instead of a your console will print using character which will look like space)

edited Aug 18 at 17:17

answered Aug 18 at 16:16

Pshemo

91.1k14127178

edited Aug 18 at 17:17

answered Aug 18 at 16:16

Pshemo

91.1k14127178

answered Aug 18 at 16:16

Pshemo

91.1k14127178

answered Aug 18 at 16:16

Pshemo

91.1k14127178

add a commentÂ |Â

up vote
11
down vote

Short version

represents character NUL, it does not equals empty string "".

Long version

When you try to create a String with empty char[10],:
```
String input = new String(new char[10]);
```
this String will contains 10 NUL character:
```
|NUL|NUL|NUL|NUL|NUL|NUL|NUL|NUL|NUL|NUL|
```

When you call input.replace("", "hello"), the NUL value() will be replaced by hello:
```
|hello|hello|hello|hello|hello|hello|hello|hello|hello|hello|
```

When you call input.replace("", "hello"), the NUL value will not be replaced since it does not match empty string "":
```
|hello|NUL|hello|NUL|hello|NUL|hello|NUL|hello|NUL|hello|NUL|hello|NUL|hello|NUL|hello|NUL|hello|NUL|hello|
```

edited Aug 18 at 19:15

answered Aug 18 at 16:19

Sun

13.1k31541

add a commentÂ |Â

up vote
11
down vote

Short version

represents character NUL, it does not equals empty string "".

Long version

When you try to create a String with empty char[10],:
```
String input = new String(new char[10]);
```
this String will contains 10 NUL character:
```
|NUL|NUL|NUL|NUL|NUL|NUL|NUL|NUL|NUL|NUL|
```

When you call input.replace("", "hello"), the NUL value() will be replaced by hello:
```
|hello|hello|hello|hello|hello|hello|hello|hello|hello|hello|
```

When you call input.replace("", "hello"), the NUL value will not be replaced since it does not match empty string "":
```
|hello|NUL|hello|NUL|hello|NUL|hello|NUL|hello|NUL|hello|NUL|hello|NUL|hello|NUL|hello|NUL|hello|NUL|hello|
```

edited Aug 18 at 19:15

answered Aug 18 at 16:19

Sun

13.1k31541

add a commentÂ |Â

up vote
11
down vote

Short version

represents character NUL, it does not equals empty string "".

Long version

When you try to create a String with empty char[10],:
```
String input = new String(new char[10]);
```
this String will contains 10 NUL character:
```
|NUL|NUL|NUL|NUL|NUL|NUL|NUL|NUL|NUL|NUL|
```

When you call input.replace("", "hello"), the NUL value() will be replaced by hello:
```
|hello|hello|hello|hello|hello|hello|hello|hello|hello|hello|
```

When you call input.replace("", "hello"), the NUL value will not be replaced since it does not match empty string "":
```
|hello|NUL|hello|NUL|hello|NUL|hello|NUL|hello|NUL|hello|NUL|hello|NUL|hello|NUL|hello|NUL|hello|NUL|hello|
```

edited Aug 18 at 19:15

answered Aug 18 at 16:19

Sun

13.1k31541

Short version

represents character NUL, it does not equals empty string "".

Long version

When you try to create a String with empty char[10],:
```
String input = new String(new char[10]);
```
this String will contains 10 NUL character:
```
|NUL|NUL|NUL|NUL|NUL|NUL|NUL|NUL|NUL|NUL|
```

When you call input.replace("", "hello"), the NUL value() will be replaced by hello:
```
|hello|hello|hello|hello|hello|hello|hello|hello|hello|hello|
```

When you call input.replace("", "hello"), the NUL value will not be replaced since it does not match empty string "":
```
|hello|NUL|hello|NUL|hello|NUL|hello|NUL|hello|NUL|hello|NUL|hello|NUL|hello|NUL|hello|NUL|hello|NUL|hello|
```

edited Aug 18 at 19:15

answered Aug 18 at 16:19

Sun

13.1k31541

edited Aug 18 at 19:15

answered Aug 18 at 16:19

Sun

13.1k31541

answered Aug 18 at 16:19

Sun

13.1k31541

answered Aug 18 at 16:19

Sun

13.1k31541

add a commentÂ |Â

up vote
7
down vote

Explanation

You are using the method String#replace(CharSequence target, CharSequence replacement) (documentation).

If invoked with an empty target character sequence replace("", replacement) it will not replace the elements in the source, but insert the replacement before every character.

This is because "" matches the positions between the characters, not the characters themselves. So every position between will be replaced, i.e. replacement is inserted.

Example:

"abc".replace("", "d") // Results in "dadbdcd"

Your string contains only the default value of char at every position, it is

using the method thus results in:

hellohellohellohellohellohellohellohellohellohello

Display

Your console probably displayed the character as whitespace, while it's actually not a whitespace but .

If I try out your code in a different console, I get:

enter image description here

Confirming that the characters are indeed not spaces but something different (i.e. ).

edited Aug 18 at 16:21

answered Aug 18 at 16:15

Zabuza

10.6k52538

replace("", ...) inserts the replacement at the end of the string too. See e.g. ideone.com/492Cml.
â€“Â Radiodef
Aug 19 at 2:45

add a commentÂ |Â

up vote
7
down vote

Explanation

You are using the method String#replace(CharSequence target, CharSequence replacement) (documentation).

If invoked with an empty target character sequence replace("", replacement) it will not replace the elements in the source, but insert the replacement before every character.

This is because "" matches the positions between the characters, not the characters themselves. So every position between will be replaced, i.e. replacement is inserted.

Example:

"abc".replace("", "d") // Results in "dadbdcd"

Your string contains only the default value of char at every position, it is

using the method thus results in:

hellohellohellohellohellohellohellohellohellohello

Display

Your console probably displayed the character as whitespace, while it's actually not a whitespace but .

If I try out your code in a different console, I get:

enter image description here

Confirming that the characters are indeed not spaces but something different (i.e. ).

edited Aug 18 at 16:21

answered Aug 18 at 16:15

Zabuza

10.6k52538

replace("", ...) inserts the replacement at the end of the string too. See e.g. ideone.com/492Cml.
â€“Â Radiodef
Aug 19 at 2:45

add a commentÂ |Â

up vote
7
down vote

Explanation

You are using the method String#replace(CharSequence target, CharSequence replacement) (documentation).

If invoked with an empty target character sequence replace("", replacement) it will not replace the elements in the source, but insert the replacement before every character.

This is because "" matches the positions between the characters, not the characters themselves. So every position between will be replaced, i.e. replacement is inserted.

Example:

"abc".replace("", "d") // Results in "dadbdcd"

Your string contains only the default value of char at every position, it is

using the method thus results in:

hellohellohellohellohellohellohellohellohellohello

Display

Your console probably displayed the character as whitespace, while it's actually not a whitespace but .

If I try out your code in a different console, I get:

enter image description here

Confirming that the characters are indeed not spaces but something different (i.e. ).

edited Aug 18 at 16:21

answered Aug 18 at 16:15

Zabuza

10.6k52538

Explanation

You are using the method String#replace(CharSequence target, CharSequence replacement) (documentation).

If invoked with an empty target character sequence replace("", replacement) it will not replace the elements in the source, but insert the replacement before every character.

This is because "" matches the positions between the characters, not the characters themselves. So every position between will be replaced, i.e. replacement is inserted.

Example:

"abc".replace("", "d") // Results in "dadbdcd"

Your string contains only the default value of char at every position, it is

using the method thus results in:

hellohellohellohellohellohellohellohellohellohello

Display

Your console probably displayed the character as whitespace, while it's actually not a whitespace but .

If I try out your code in a different console, I get:

enter image description here

Confirming that the characters are indeed not spaces but something different (i.e. ).

edited Aug 18 at 16:21

answered Aug 18 at 16:15

Zabuza

10.6k52538

edited Aug 18 at 16:21

answered Aug 18 at 16:15

Zabuza

10.6k52538

answered Aug 18 at 16:15

Zabuza

10.6k52538

answered Aug 18 at 16:15

Zabuza

10.6k52538

replace("", ...) inserts the replacement at the end of the string too. See e.g. ideone.com/492Cml.
â€“Â Radiodef
Aug 19 at 2:45

add a commentÂ |Â

replace("", ...) inserts the replacement at the end of the string too. See e.g. ideone.com/492Cml.
â€“Â Radiodef
Aug 19 at 2:45

replace("", ...) inserts the replacement at the end of the string too. See e.g. ideone.com/492Cml.
â€“Â Radiodef
Aug 19 at 2:45

add a commentÂ |Â

up vote
3
down vote

char's default value is u0000 which can also be represented as . So your new char[10] contains 10 s.

In the first statement you clearly replace with "hello". But in the second statement you leave out the default value. Which your IDE output chooses to show as a space.

answered Aug 18 at 16:28

Roshana Pitigala

3,57162342

add a commentÂ |Â

up vote
3
down vote

char's default value is u0000 which can also be represented as . So your new char[10] contains 10 s.

In the first statement you clearly replace with "hello". But in the second statement you leave out the default value. Which your IDE output chooses to show as a space.

answered Aug 18 at 16:28

Roshana Pitigala

3,57162342

add a commentÂ |Â

up vote
3
down vote

char's default value is u0000 which can also be represented as . So your new char[10] contains 10 s.

In the first statement you clearly replace with "hello". But in the second statement you leave out the default value. Which your IDE output chooses to show as a space.

answered Aug 18 at 16:28

Roshana Pitigala

3,57162342

char's default value is u0000 which can also be represented as . So your new char[10] contains 10 s.

In the first statement you clearly replace with "hello". But in the second statement you leave out the default value. Which your IDE output chooses to show as a space.

answered Aug 18 at 16:28

Roshana Pitigala

3,57162342

answered Aug 18 at 16:28

Roshana Pitigala

3,57162342

answered Aug 18 at 16:28

Roshana Pitigala

3,57162342

answered Aug 18 at 16:28

Roshana Pitigala

3,57162342

add a commentÂ |Â

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