The constructor ... is not visible

When you invoke the private constructor of a class in another class, you’ll get the error message “The constructor ... is not visible”. And when the private constructor of a super class is invoked from the subclass implicitly or explicitly, you’ll get the following: Implicit super constructor ... is not visible for default constructor. Must define an explicit constructor. Implicit super constructor...

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java.lang.UnsupportedOperationException at java.util.AbstractList.remove

When you create a java.util.List object from an array using Arrays.asList method and after that if you try to clear or remove the elements from the list you'll get this run time error. The reason is that Arrays.asList method returns a fixed-size list backed by the specified array. See in the example code below: int[] myArray = {5,10,15,20}; List intList = Arrays.asList(myArray); ...

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Resource leak: 'scanner' is never closed

If you do not close the java.util.Scanner object after reading data, you can get an warning saying "Resource leak: 'scanner' is never closed". In the code below see that the Scanner object is closed in a finally block after reading all inputs using the Scanner object. int number1, number2; Scanner scanner = new Scanner(System.in); try { System.out.println("Ener the first number"); ...

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Dimensions expected after this token / '[' expected

Java error "Dimensions expected after this token" or " '[' expected " can occur while creating array elements or allocating memory using the keyword new. If the square brackets [] are not used properly, you can get this error message. See the code below: int myArray[]=new int{10,20,30,40}; Here this is a syntax error. You have to put square brackets [] after new int. To initialize an array...

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Cannot invoke length() on the array type

The error message "Cannot invoke length() on the array type" or "cannot find symbol ... method length()" is related with the use of array. Java array has a built in property length which is a variable, not method. If you put parenthesis () after the array property length, you'll get this error. See the example below: int[] number = {5,10,15}; for(int i=0; i<number.length(); i++) {    ...

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