Why is my Java code not compiling?

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  11 years ago

  by srbruno

  Sal Bruno

  San Ramon, United States

  Joined 11 years ago

  I am new to Java and need to know how to correct this function call parameter passing compiling error. Any ideas?

  List.java compiles and here is the code. //---------------------------------------------------------------------------- // List.java //---------------------------------------------------------------------------- class List { private class Node { int col; double val; Node next, prev;

        Node (int c, double v) { col = c; val = v; next = prev = null; } 
  
        public String toString() { 
           return String.format (" (%2d, %5.2f)", col, val); 
        } 
  
        public boolean equals(Node E) { return (this.val == E.val); } 
        } 
  
     private Node front, back, current; 
     private int row, length; 
  
     List(int r) { front = back = current = null; row = r; length = 0; } 
  
     void insertAfterLast(Node N) 
     {  Node node = new Node(N.col, N.val); 
  
        if ( this.length == 0 ) 
        { this.front = this.back = node; 
        }else { 
           node.prev = this.back; 
           this.back.next = node; 
           this.back = node; 
           this.current = node; 
        } 
        this.length++; 
     } 
  
     public String toString() 
     {  String str = ""; 
        for(Node N = front; N != null;  N = N.next) 
        {  if ( N == front ) { str = String.format ("%3d:", row); } 
           str += N.toString() + (N.next==null?"\n":""); 
        } 
        return str; 
     } 
  }
  

  ListTest.Java does not compile. Here are the error and code.

  -bash-3.00$ javac ListTest.java ListTest.java:20: non-static variable this cannot be referenced from a static context Entry Ea = new Entry(0, 0.0); ^ ListTest.java:24: insertAfterLast(List.Node) in List cannot be applied to (ListTest.Entry) A.insertAfterLast(Ea); ^ ListTest.java:26: insertAfterLast(List.Node) in List cannot be applied to (ListTest.Entry) B.insertAfterLast(Ea); ^ ListTest.java:28: insertAfterLast(List.Node) in List cannot be applied to (ListTest.Entry) B.insertAfterLast(Ea); ^ 4 errors

  //---------------------------------------------------------------------------- 
  // ListTest.java - A test client for the List ADT 
  //---------------------------------------------------------------------------- 
  class ListTest 
  { 
     private class Entry 
     {  int col; 
        double val; 
        Entry next, prev; 
  
        // Entry Constructor 
        Entry (int c, double v) { col = c; val = v; next = prev = null; } 
     } 
  
     public static void main(String[] args) 
     {  int i; 
        List A = new List(1); 
        List B = new List(2); 
  
        Entry Ea = new Entry(0, 0.0); 
        for(i=1; i<=4; i++){ 
           Ea.col = i; 
           Ea.val = Double.parseDouble(Integer.toString(i)); 
           A.insertAfterLast(Ea); 
           Ea.val = Double.parseDouble(Integer.toString(10-2*i)); 
           B.insertAfterLast(Ea); 
           Ea.val = Double.parseDouble(Integer.toString(9-2*i)); 
           B.insertAfterLast(Ea); 
        } 
  
        System.out.println(" "); 
        System.out.println("Print Lists A and B which have been initialized");       
        System.out.println("A = " + A); 
        System.out.println("B = " + B); 
  
     } 
  }
  

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