What is operating system?why is it required

Assume that you have an array of integers named a. which of these code segments print the same results? int i = 1; while(i < a.length) { system.out.println(a[i]); i++; } int i; for (i = 0; i < a.length; i++) { system.out.println(a[i]); } for (int i : a) { system.out.println(i); } i and ii only ii and iii only i and iii only all three print the same results. all three print different results.

Write the quartstogallons java class that declares a named constant to hold the number of quarts in a gallon (4). also declare a variable to represent the number of quarts needed for a painting job, and assign an appropriate value—for example, 18. compute and display the number of gallons and quarts needed for the job. display explanatory text with the values, for example:

Write a program that uses a widgetviewer object to do the following: generate two random integers between 1 and 9 (inclusive). name one of them x, the other y. display them to the user using jlabel objects. create a jlabel object displaying the text "enter an operation number." create a jtextfield for the user's input. create a jbutton displaying the text "press here when you've entered your operation." use addandwait to add it to the widgetviewer object. when the user clicks the jbutton, evaluate operation in the following order to determine the one and only mathematical operation to perform on x and y. use a jlabel to display the result. if operation is between 1 and 10 inclusive, add x and y. if operation is evenly divisible by 4, subtract y from x. if operation is evenly divisible by 5, use integer division to divide y into x. if operation is an even number, use floating point division to divide y into x. if none of the other tests on operation apply, multiply x and y. note: operation can be negative or zero.