java - My delete method to remove a specific Node with X age value will not work -

this code, please reference main method , delete method, other methods included show full program. have heard java takes method arguments pass value, issue, , object's properties pass-by-reference.

so change node.age, since age property, cannot make node equal node = node.next? have been @ while, trying learn how different operations , have been stuck on this. if-statement went through, headnode did not equate headnode.next wanted to:

public class node {     int age;     node next;     node previous;      public static void main (string [] args) {         node firstnode = new node(18);         node t = firstnode;          node randomfatnode = new node();          for(int = 0; < 30; += 3) {             node tempnode = new node(i + 21);             firstnode.next = tempnode;             tempnode.previous = firstnode;             firstnode = tempnode;         }          node tailnode = firstnode;          firstnode = t;          traverseforward(firstnode);         //prints out: traversal forward -> 18 -> 21 -> 24 -> 27 -> 30 -> 33 -> 36 -> 39 -> 42 -> 45 -> 48 -> null           deletenode(firstnode, 18); //does not delete first node, has age of 18.          traverseforward(firstnode);         //prints out: traversal forward -> 18 -> 21 -> 24 -> 27 -> 30 -> 33 -> 36 -> 39 -> 42 -> 45 -> 48 -> null     }      public node() {         this.age = 20;         this.next = null;         this.previous = null;     }      public node(int inputage) {         this.age = inputage;         this.next = null;         this.previous = null;     }      public static void traverseforward(node headnode) {         system.out.print("traversal forward -> ");         node usethisfortestnode = headnode;         while(usethisfortestnode != null) {             system.out.print(usethisfortestnode.age + " -> ");             usethisfortestnode = usethisfortestnode.next;         }         system.out.print("null ");         system.out.println();     }      public static void deletenode(node headnode, int keytodelete) {         node temp = headnode;         if(temp != null && temp.age == keytodelete)  {             headnode = headnode.next;             system.out.println("test");             //printed out test see if if statement went through. did, node in linked list remained unchanged.         }     }      // other methods } 

you need make firstnode class field.