Java Core Classes and Threads

The NumberFormat class belongs to java.text package. It has three methods that yield standard formats for numbers, currency values and percentage values.

Both the statements are correct. The methods valueOf() and toString() belong to String class. The valueOf() method is a static method, so it is always called by using the class name String and the method toString() is overridden in wrapper classes, such as Integer and Double.

This method of Observable class returns true value if the invoking object has been modified and false if it has not.

The constructor StringBuffer() of a StringBuffer class creates a StringBuffer with the capacity of 16 characters by default.

This method is used to extract a single character from a string.

This method searches for the first occurrence of a character or substring.

This method is used to pre-allocate a space for a certain number of characters, after a StringBuffer has been constructed. This method determines whether a given string begins with a specified string or not.

This method returns the value of the invoking object of the type 'byte'.

This method is used to find the execution time of the various parts of the program.

This method returns the value true, if the invoking object contains infinite values.

This method displays the call stack for the thread.

This method determines whether the string in the question ends with a specified string or not.

If we want to convert all the characters in a string object into a character array, we use the method toCharArray().

This method returns the name of the invoking package.

This method returns the number of threads in the group, along with a group, for which this thread is a parent.