Java sort List of objects with a hierarchy alphabetically

I have an entity called Item. Item can have parents and children.

Each Item has the following methods:

getParent() --> returns an Item

getChildren() --> returns a List<Item>

isLeaf() --> returns a Boolean

getName() --> returns a String

Each level in the hierarchy is a level in a construction site, for example level 1 is House 1, level 2 is Floor 1, level 3 is Room and level 4 is Window.

I have a List<Item and I need to sort them like this:

Item 1 (House 1 > Floor 1 > Room 1 > Bath)

Item 2 (House 1 > Floor 1 > Room 2 > Basement)

Item 3 (House 1 > Floor 1 > Room 2 > Door)

Item 4 (House 1 > Floor 1 > Room 2 > Window)

Item 5 (House 1 > Floor 2 > Room 1 > Door)

I think I need some kind of recursive function but I can't imagine how it has to be.

I've already researched for sorting objects with a hierarchy in Java but I don't find anything similar to my case.

I would appreciate any help and sorry if the question is not clear 100% but it is quite hard to describe.

Thanks.

edited Nov 13 '18 at 13:46

rghome

4,69152540

asked Nov 13 '18 at 10:44

Ale

82322144

Basically you want to sort the leaves then? I would imagine that you would sort when adding the elements to the house object and then do a depth first lookup of the leaves
– SBylemans
Nov 13 '18 at 11:00

What is an entity? You can't create a new class called Object. There is already an important class in Java called Object ;)
– flakes
Nov 13 '18 at 11:45

@flakes thanks for your comment but I don't think that's important and it doesn't add anything to the question. The real name of the "Object" is Objekt (Object in German). I omitted that detail to avoid confusing people with irrelevant information. If you feel happier I can rename Object to Item
– Ale
Nov 13 '18 at 11:55

You need to provide some code. It is unclear to me what is your implementation. Are all entities of type item (houses, floors, rooms) or are those different classes? Do they implement/extend item class?
– Amongalen
Nov 13 '18 at 12:03

When discussing class design/method implementation, having a class name is pretty crucial for communication! Further, you should be providing some code in your questions to show us at what point your stuck. Define as much of the solution as you can and you'll find that people understand your problem better and provide answers closer to what you expect. As an aside, names like Objekt and Item are pretty opaque names for a class.. try something more meaningful (makes it obvious as to the actual purpose, HouseNode, FloorplanTree, etc). Good naming is paramount to clean maintainable code
– flakes
Nov 13 '18 at 12:53

add a comment |

I have an entity called Item. Item can have parents and children.

Each Item has the following methods:

getParent() --> returns an Item

getChildren() --> returns a List<Item>

isLeaf() --> returns a Boolean

getName() --> returns a String

Each level in the hierarchy is a level in a construction site, for example level 1 is House 1, level 2 is Floor 1, level 3 is Room and level 4 is Window.

I have a List<Item and I need to sort them like this:

Item 1 (House 1 > Floor 1 > Room 1 > Bath)

Item 2 (House 1 > Floor 1 > Room 2 > Basement)

Item 3 (House 1 > Floor 1 > Room 2 > Door)

Item 4 (House 1 > Floor 1 > Room 2 > Window)

Item 5 (House 1 > Floor 2 > Room 1 > Door)

I think I need some kind of recursive function but I can't imagine how it has to be.

I've already researched for sorting objects with a hierarchy in Java but I don't find anything similar to my case.

I would appreciate any help and sorry if the question is not clear 100% but it is quite hard to describe.

Thanks.

edited Nov 13 '18 at 13:46

rghome

4,69152540

asked Nov 13 '18 at 10:44

Ale

82322144

Basically you want to sort the leaves then? I would imagine that you would sort when adding the elements to the house object and then do a depth first lookup of the leaves
– SBylemans
Nov 13 '18 at 11:00

What is an entity? You can't create a new class called Object. There is already an important class in Java called Object ;)
– flakes
Nov 13 '18 at 11:45

@flakes thanks for your comment but I don't think that's important and it doesn't add anything to the question. The real name of the "Object" is Objekt (Object in German). I omitted that detail to avoid confusing people with irrelevant information. If you feel happier I can rename Object to Item
– Ale
Nov 13 '18 at 11:55

You need to provide some code. It is unclear to me what is your implementation. Are all entities of type item (houses, floors, rooms) or are those different classes? Do they implement/extend item class?
– Amongalen
Nov 13 '18 at 12:03

When discussing class design/method implementation, having a class name is pretty crucial for communication! Further, you should be providing some code in your questions to show us at what point your stuck. Define as much of the solution as you can and you'll find that people understand your problem better and provide answers closer to what you expect. As an aside, names like Objekt and Item are pretty opaque names for a class.. try something more meaningful (makes it obvious as to the actual purpose, HouseNode, FloorplanTree, etc). Good naming is paramount to clean maintainable code
– flakes
Nov 13 '18 at 12:53

add a comment |

I have an entity called Item. Item can have parents and children.

Each Item has the following methods:

getParent() --> returns an Item

getChildren() --> returns a List<Item>

isLeaf() --> returns a Boolean

getName() --> returns a String

Each level in the hierarchy is a level in a construction site, for example level 1 is House 1, level 2 is Floor 1, level 3 is Room and level 4 is Window.

I have a List<Item and I need to sort them like this:

Item 1 (House 1 > Floor 1 > Room 1 > Bath)

Item 2 (House 1 > Floor 1 > Room 2 > Basement)

Item 3 (House 1 > Floor 1 > Room 2 > Door)

Item 4 (House 1 > Floor 1 > Room 2 > Window)

Item 5 (House 1 > Floor 2 > Room 1 > Door)

I think I need some kind of recursive function but I can't imagine how it has to be.

I've already researched for sorting objects with a hierarchy in Java but I don't find anything similar to my case.

I would appreciate any help and sorry if the question is not clear 100% but it is quite hard to describe.

Thanks.

edited Nov 13 '18 at 13:46

rghome

4,69152540

asked Nov 13 '18 at 10:44

Ale

82322144

I have an entity called Item. Item can have parents and children.

Each Item has the following methods:

getParent() --> returns an Item

getChildren() --> returns a List<Item>

isLeaf() --> returns a Boolean

getName() --> returns a String

Each level in the hierarchy is a level in a construction site, for example level 1 is House 1, level 2 is Floor 1, level 3 is Room and level 4 is Window.

I have a List<Item and I need to sort them like this:

Item 1 (House 1 > Floor 1 > Room 1 > Bath)

Item 2 (House 1 > Floor 1 > Room 2 > Basement)

Item 3 (House 1 > Floor 1 > Room 2 > Door)

Item 4 (House 1 > Floor 1 > Room 2 > Window)

Item 5 (House 1 > Floor 2 > Room 1 > Door)

I think I need some kind of recursive function but I can't imagine how it has to be.

I've already researched for sorting objects with a hierarchy in Java but I don't find anything similar to my case.

I would appreciate any help and sorry if the question is not clear 100% but it is quite hard to describe.

Thanks.

java sorting recursion hierarchy comparator

edited Nov 13 '18 at 13:46

rghome

4,69152540

asked Nov 13 '18 at 10:44

Ale

82322144

edited Nov 13 '18 at 13:46

rghome

4,69152540

asked Nov 13 '18 at 10:44

Ale

82322144

edited Nov 13 '18 at 13:46

rghome

4,69152540

edited Nov 13 '18 at 13:46

rghome

4,69152540

edited Nov 13 '18 at 13:46

rghome

4,69152540

asked Nov 13 '18 at 10:44

Ale

82322144

asked Nov 13 '18 at 10:44

Ale

82322144

asked Nov 13 '18 at 10:44

Ale

82322144

Basically you want to sort the leaves then? I would imagine that you would sort when adding the elements to the house object and then do a depth first lookup of the leaves
– SBylemans
Nov 13 '18 at 11:00

What is an entity? You can't create a new class called Object. There is already an important class in Java called Object ;)
– flakes
Nov 13 '18 at 11:45

@flakes thanks for your comment but I don't think that's important and it doesn't add anything to the question. The real name of the "Object" is Objekt (Object in German). I omitted that detail to avoid confusing people with irrelevant information. If you feel happier I can rename Object to Item
– Ale
Nov 13 '18 at 11:55

You need to provide some code. It is unclear to me what is your implementation. Are all entities of type item (houses, floors, rooms) or are those different classes? Do they implement/extend item class?
– Amongalen
Nov 13 '18 at 12:03

When discussing class design/method implementation, having a class name is pretty crucial for communication! Further, you should be providing some code in your questions to show us at what point your stuck. Define as much of the solution as you can and you'll find that people understand your problem better and provide answers closer to what you expect. As an aside, names like Objekt and Item are pretty opaque names for a class.. try something more meaningful (makes it obvious as to the actual purpose, HouseNode, FloorplanTree, etc). Good naming is paramount to clean maintainable code
– flakes
Nov 13 '18 at 12:53

add a comment |

Basically you want to sort the leaves then? I would imagine that you would sort when adding the elements to the house object and then do a depth first lookup of the leaves
– SBylemans
Nov 13 '18 at 11:00

What is an entity? You can't create a new class called Object. There is already an important class in Java called Object ;)
– flakes
Nov 13 '18 at 11:45

@flakes thanks for your comment but I don't think that's important and it doesn't add anything to the question. The real name of the "Object" is Objekt (Object in German). I omitted that detail to avoid confusing people with irrelevant information. If you feel happier I can rename Object to Item
– Ale
Nov 13 '18 at 11:55

You need to provide some code. It is unclear to me what is your implementation. Are all entities of type item (houses, floors, rooms) or are those different classes? Do they implement/extend item class?
– Amongalen
Nov 13 '18 at 12:03

When discussing class design/method implementation, having a class name is pretty crucial for communication! Further, you should be providing some code in your questions to show us at what point your stuck. Define as much of the solution as you can and you'll find that people understand your problem better and provide answers closer to what you expect. As an aside, names like Objekt and Item are pretty opaque names for a class.. try something more meaningful (makes it obvious as to the actual purpose, HouseNode, FloorplanTree, etc). Good naming is paramount to clean maintainable code
– flakes
Nov 13 '18 at 12:53

Basically you want to sort the leaves then? I would imagine that you would sort when adding the elements to the house object and then do a depth first lookup of the leaves
– SBylemans
Nov 13 '18 at 11:00

What is an entity? You can't create a new class called Object. There is already an important class in Java called Object ;)
– flakes
Nov 13 '18 at 11:45

@flakes thanks for your comment but I don't think that's important and it doesn't add anything to the question. The real name of the "Object" is Objekt (Object in German). I omitted that detail to avoid confusing people with irrelevant information. If you feel happier I can rename Object to Item
– Ale
Nov 13 '18 at 11:55

You need to provide some code. It is unclear to me what is your implementation. Are all entities of type item (houses, floors, rooms) or are those different classes? Do they implement/extend item class?
– Amongalen
Nov 13 '18 at 12:03

When discussing class design/method implementation, having a class name is pretty crucial for communication! Further, you should be providing some code in your questions to show us at what point your stuck. Define as much of the solution as you can and you'll find that people understand your problem better and provide answers closer to what you expect. As an aside, names like Objekt and Item are pretty opaque names for a class.. try something more meaningful (makes it obvious as to the actual purpose, HouseNode, FloorplanTree, etc). Good naming is paramount to clean maintainable code
– flakes
Nov 13 '18 at 12:53

add a comment |

2 Answers
2

active

oldest

votes

It would indeed be recursive. The trouble is that a simple recursive compare would only work if the two nodes were on the same level.

// Same level compare

int compareSameLevel(Item item) {

    int c = 0;

    if (this.getParent != null) {

        c = compare(this.getParent(), item.getParent());

    }

    return (c != 0) ? c : getName().compare(item.getName());

}

But you could adjust the levels to find a common level and assume that the children go after the parent:

// Compare on any level

int compare(Item item) {

    Item thisItem = this;

    int thisLevel = thisItem.level();

    int itemLevel = item.level();



    for (int i = thisLevel; i > itemLevel; i--) {

        thisItem = thisItem.getParent();

    }



    for (int j = itemLevel; j > thisLevel; j--) {

        item = item.getParent();

    }



    int c = compareSameLevel(thisItem, item);



    return c != 0 ? c : (thisLevel > itemLevel ? -1 : 1);

}

This is just to give you an idea. It is not tested or compiled.

answered Nov 13 '18 at 12:37

rghome

4,69152540

add a comment |

-1

Pseudo code: Try like this

    private static void printChildElements(List<Object> childNodes) {

    for(Object childNode : childNodes) {



        List<Object > childElements = childNode .....;

        if(childElements.size() > 0) {

            printChildElements( childElements);

        }

    }

answered Nov 13 '18 at 12:23

Prakash N

347

The question is about sorting, not about printing the whole tree.
– rghome
Nov 13 '18 at 12:41

add a comment |

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2 Answers
2

active

oldest

votes

2 Answers
2

active

oldest

votes

It would indeed be recursive. The trouble is that a simple recursive compare would only work if the two nodes were on the same level.

// Same level compare

int compareSameLevel(Item item) {

    int c = 0;

    if (this.getParent != null) {

        c = compare(this.getParent(), item.getParent());

    }

    return (c != 0) ? c : getName().compare(item.getName());

}

But you could adjust the levels to find a common level and assume that the children go after the parent:

// Compare on any level

int compare(Item item) {

    Item thisItem = this;

    int thisLevel = thisItem.level();

    int itemLevel = item.level();



    for (int i = thisLevel; i > itemLevel; i--) {

        thisItem = thisItem.getParent();

    }



    for (int j = itemLevel; j > thisLevel; j--) {

        item = item.getParent();

    }



    int c = compareSameLevel(thisItem, item);



    return c != 0 ? c : (thisLevel > itemLevel ? -1 : 1);

}

This is just to give you an idea. It is not tested or compiled.

answered Nov 13 '18 at 12:37

rghome

4,69152540

add a comment |

It would indeed be recursive. The trouble is that a simple recursive compare would only work if the two nodes were on the same level.

// Same level compare

int compareSameLevel(Item item) {

    int c = 0;

    if (this.getParent != null) {

        c = compare(this.getParent(), item.getParent());

    }

    return (c != 0) ? c : getName().compare(item.getName());

}

But you could adjust the levels to find a common level and assume that the children go after the parent:

// Compare on any level

int compare(Item item) {

    Item thisItem = this;

    int thisLevel = thisItem.level();

    int itemLevel = item.level();



    for (int i = thisLevel; i > itemLevel; i--) {

        thisItem = thisItem.getParent();

    }



    for (int j = itemLevel; j > thisLevel; j--) {

        item = item.getParent();

    }



    int c = compareSameLevel(thisItem, item);



    return c != 0 ? c : (thisLevel > itemLevel ? -1 : 1);

}

This is just to give you an idea. It is not tested or compiled.

answered Nov 13 '18 at 12:37

rghome

4,69152540

add a comment |

It would indeed be recursive. The trouble is that a simple recursive compare would only work if the two nodes were on the same level.

// Same level compare

int compareSameLevel(Item item) {

    int c = 0;

    if (this.getParent != null) {

        c = compare(this.getParent(), item.getParent());

    }

    return (c != 0) ? c : getName().compare(item.getName());

}

But you could adjust the levels to find a common level and assume that the children go after the parent:

// Compare on any level

int compare(Item item) {

    Item thisItem = this;

    int thisLevel = thisItem.level();

    int itemLevel = item.level();



    for (int i = thisLevel; i > itemLevel; i--) {

        thisItem = thisItem.getParent();

    }



    for (int j = itemLevel; j > thisLevel; j--) {

        item = item.getParent();

    }



    int c = compareSameLevel(thisItem, item);



    return c != 0 ? c : (thisLevel > itemLevel ? -1 : 1);

}

This is just to give you an idea. It is not tested or compiled.

answered Nov 13 '18 at 12:37

rghome

4,69152540

It would indeed be recursive. The trouble is that a simple recursive compare would only work if the two nodes were on the same level.

// Same level compare

int compareSameLevel(Item item) {

    int c = 0;

    if (this.getParent != null) {

        c = compare(this.getParent(), item.getParent());

    }

    return (c != 0) ? c : getName().compare(item.getName());

}

But you could adjust the levels to find a common level and assume that the children go after the parent:

// Compare on any level

int compare(Item item) {

    Item thisItem = this;

    int thisLevel = thisItem.level();

    int itemLevel = item.level();



    for (int i = thisLevel; i > itemLevel; i--) {

        thisItem = thisItem.getParent();

    }



    for (int j = itemLevel; j > thisLevel; j--) {

        item = item.getParent();

    }



    int c = compareSameLevel(thisItem, item);



    return c != 0 ? c : (thisLevel > itemLevel ? -1 : 1);

}

This is just to give you an idea. It is not tested or compiled.

answered Nov 13 '18 at 12:37

rghome

4,69152540

answered Nov 13 '18 at 12:37

rghome

4,69152540

answered Nov 13 '18 at 12:37

rghome

4,69152540

answered Nov 13 '18 at 12:37

rghome

4,69152540

add a comment |

-1

Pseudo code: Try like this

    private static void printChildElements(List<Object> childNodes) {

    for(Object childNode : childNodes) {



        List<Object > childElements = childNode .....;

        if(childElements.size() > 0) {

            printChildElements( childElements);

        }

    }

answered Nov 13 '18 at 12:23

Prakash N

347

The question is about sorting, not about printing the whole tree.
– rghome
Nov 13 '18 at 12:41

add a comment |

-1

Pseudo code: Try like this

    private static void printChildElements(List<Object> childNodes) {

    for(Object childNode : childNodes) {



        List<Object > childElements = childNode .....;

        if(childElements.size() > 0) {

            printChildElements( childElements);

        }

    }

answered Nov 13 '18 at 12:23

Prakash N

347

The question is about sorting, not about printing the whole tree.
– rghome
Nov 13 '18 at 12:41

add a comment |

-1

Pseudo code: Try like this

    private static void printChildElements(List<Object> childNodes) {

    for(Object childNode : childNodes) {



        List<Object > childElements = childNode .....;

        if(childElements.size() > 0) {

            printChildElements( childElements);

        }

    }

answered Nov 13 '18 at 12:23

Prakash N

347

Pseudo code: Try like this

    private static void printChildElements(List<Object> childNodes) {

    for(Object childNode : childNodes) {



        List<Object > childElements = childNode .....;

        if(childElements.size() > 0) {

            printChildElements( childElements);

        }

    }

answered Nov 13 '18 at 12:23

Prakash N

347

answered Nov 13 '18 at 12:23

Prakash N

347

answered Nov 13 '18 at 12:23

Prakash N

347

answered Nov 13 '18 at 12:23

Prakash N

347

The question is about sorting, not about printing the whole tree.
– rghome
Nov 13 '18 at 12:41

add a comment |

The question is about sorting, not about printing the whole tree.
– rghome
Nov 13 '18 at 12:41

The question is about sorting, not about printing the whole tree.
– rghome
Nov 13 '18 at 12:41

add a comment |

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