JProgressBar Class in Java

A component that visually displays the progress of some task. As the task progresses towards completion, the progress bar displays the task's percentage of completion. This percentage is typically represented visually by a rectangle which starts out empty and gradually becomes filled in as the task progresses. In addition, the progress bar can display a textual representation of this percentage.

Syntax of JProgressBar

JProgressBar uses a BoundedRangeModel as its data model, with the value property representing the "current" state of the task, and the minimum and maximum properties representing the beginning and end points, respectively.

To indicate that a task of unknown length is executing, you can put a progress bar into indeterminate mode. While the bar is in indeterminate mode, it animates constantly to show that work is occurring. As soon as you can determine the task's length and amount of progress, you should update the progress bar's value and switch it back to determinate mode.

Here is an example of creating a progress bar, where task is an object (representing some piece of work) which returns information about the progress of the task:

progressBar = new JProgressBar(0, task.getLengthOfTask());
progressBar.setValue(0);
progressBar.setStringPainted(true);
   

Here is an example of querying the current state of the task, and using the returned value to update the progress bar:

progressBar.setValue(task.getCurrent());
   

Here is an example of putting a progress bar into indeterminate mode, and then switching back to determinate mode once the length of the task is known:

progressBar = new JProgressBar();
...//when the task of (initially) unknown length begins:
progressBar.setIndeterminate(true);
...//do some work; get length of task...
progressBar.setMaximum(newLength);
progressBar.setValue(newValue);
progressBar.setIndeterminate(false);
   

Though Swing is not thread safe.

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