Dynamic value initialization in Array in java

Question

In my code I have one vairable:

public Edge[] adjacencies;

now for initialization array is something like this:

     v0.adjacencies = new Edge[] {
        new Edge(v1, distance[0][1]),
        new Edge(v2, distance[0][2]),
        new Edge(v3, distance[0][3]),
        new Edge(v4, distance[0][4]),
        new Edge(v5, distance[0][5]),
        new Edge(v6, distance[0][6]),
        new Edge(v7, distance[0][7]) 
        };

but I want to give dynamic initialization something like this:

 v0.adjacencies = new Edge[] {
    for(int i=1;i<8;i++)    
         new Edge("v"+i, distance[0][i]); 
 };

Sounds like v[i] needs to be an array, instead of v0, v1, v2 etc. — Dawood ibn Kareem
– Dawood ibn Kareem, Commented Oct 23, 2013 at 4:55
I certainly doubt if v* are strings, as assumed by everybody who has posted the answer. All those v1, v2.. seem to be some class(I guess Vertex) objects. — Rahul
– Rahul, Commented Oct 23, 2013 at 5:01

mau · Accepted Answer · 2013-10-23 04:56:07Z

1

One way to do this dynamically is to create the array with the variable length.

length = 8; 
v0.adjecencies = new Edge[length];
for(int i=1;i<length;i++)    
  v0.adjecencies[i-1] = new Edge("v"+i, distance[0][i]);

answered Oct 23, 2013 at 4:56

mau

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Comments

npinti · Accepted Answer · 2013-10-23 04:56:11Z

0

How about something like this:

v0.adjacencies = new Edge[7];
for(int i = 1; 1 < 8; i++)
{
    v0.adjacencies[i - 1] = new Edge("v"+i, distance[0][i]); 
}

I'm assuming that v1, v2, etc are strings of the form v1, v2, etc.

answered Oct 23, 2013 at 4:56

npinti

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Comments

Terry Li · Accepted Answer · 2013-10-23 05:06:58Z

0

Vertex[] vertices = {v1,v2,v3,v4,v5,v6,v7};
v0.adjacencies = new Edge[7];
for(int i=1;i<8;i++) {   
  v0.adjacencies[i-1] = new Edge(vertices[i-1], distance[0][i]); 
}

Try this.

Update: I assume those v1, v2, ... are objects of class Vertex (whatever you call it) and update the code accordingly.

edited Oct 23, 2013 at 5:06

answered Oct 23, 2013 at 4:55

Terry Li

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3 Comments

user2908533 Over a year ago

java.lang.NullPointerException is coming

user2908533 Over a year ago

after that when I am calling from one function computePaths(v0); NullPointerException is coming

Terry Li Over a year ago

@user2908533 Updated. See if it fixes the issue.

Manish Doshi · Accepted Answer · 2013-10-23 05:40:40Z

0

You will want to look into the java.util package, specifically the ArrayList class. It has methods such as .add() .remove() .indexof() .contains() .toArray(), and more

answered Oct 23, 2013 at 5:40

Manish Doshi

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Comments

Dawood ibn Kareem · Accepted Answer · 2013-10-23 06:34:18Z

0

Forget all about your variables v1, v2 and so on. Just keep them all in an array to start with.

Vertex[] vertices = new Vertex[8];
for (int i = 0; i < 8; i++) {
    vertices[i] = new Vertex();
}

vertices[0].adjacencies = new Edge[7];
for (int i = 1; i < 8; i++) {
    vertices[0].adjacencies[i - 1] = new Edge(vertices[i], distance[0][i]);
}

answered Oct 23, 2013 at 6:34

Dawood ibn Kareem

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