Question

Let’s assume that there are three methods in a class as follows and I need to call each method one after another one, but as each method is running on a separate Thread I get errors, please tell me a way to call each of following methods as,

.....
methodOne();
methodTwo();
methodTree();
.....

public Class Test{

public void methodOne(){

    new Thread(new Runnable(){
        @Override
            public void run() {
            .....
        }
    }).start();

}

public void methodTwo(){

    new Thread(new Runnable(){
        @Override
            public void run() {
            .....
        }
    }).start();

}


public void methodThree(){

    new Thread(new Runnable(){
        @Override
            public void run() {
            .....
        }
    }).start();

}

}

I get following errors

java.util.ConcurrentModificationException
        at java.util.LinkedList$ListItr.checkForComodification(LinkedList.java:778)
        at java.util.LinkedList$ListItr.next(LinkedList.java:713)
        at Manufacturing.MonthEnd.FinishMonth.fillPreviousMonthBalanceRec(FinishMonth.java:141)
        at Manufacturing.MonthEnd.FinishMonth.closeMonth(FinishMonth.java:52)
        at Manufacturing.MonthControllerView.btnCloseMonthActionPerformed(MonthControllerView.java:588)
        at Manufacturing.MonthControllerView.access$400(MonthControllerView.java:28)
        at Manufacturing.MonthControllerView$6.actionPerformed(MonthControllerView.java:465)
        at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:2012)
        at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2335)
        at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:404)
        at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:259)
        at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:253)
        at java.awt.Component.processMouseEvent(Component.java:6203)
        at javax.swing.JComponent.processMouseEvent(JComponent.java:3267)
        at java.awt.Component.processEvent(Component.java:5968)
        at java.awt.Container.processEvent(Container.java:2105)
        at java.awt.Component.dispatchEventImpl(Component.java:4564)
        at java.awt.Container.dispatchEventImpl(Container.java:2163)
        at java.awt.Component.dispatchEvent(Component.java:4390)
        at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4461)
        at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4125)
        at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4055)
        at java.awt.Container.dispatchEventImpl(Container.java:2149)
        at java.awt.Window.dispatchEventImpl(Window.java:2478)
        at java.awt.Component.dispatchEvent(Component.java:4390)
        at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:649)
        at java.awt.EventQueue.access$000(EventQueue.java:96)
        at java.awt.EventQueue$1.run(EventQueue.java:608)
        at java.awt.EventQueue$1.run(EventQueue.java:606)
        at java.security.AccessController.doPrivileged(Native Method)
        at java.security.AccessControlContext$1.doIntersectionPrivilege(AccessControlContext.java:105)
        at java.security.AccessControlContext$1.doIntersectionPrivilege(AccessControlContext.java:116)
        at java.awt.EventQueue$2.run(EventQueue.java:622)
        at java.awt.EventQueue$2.run(EventQueue.java:620)
        at java.security.AccessController.doPrivileged(Native Method)
        at java.security.AccessControlContext$1.doIntersectionPrivilege(AccessControlContext.java:105)
        at java.awt.EventQueue.dispatchEvent(EventQueue.java:619)
        at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:275)
        at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:200)
        at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:190)
        at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:185)
        at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:177)
        at java.awt.EventDispatchThread.run(EventDispatchThread.java:138)

Answer 1

You can use method

new Thread().join();

And wait for previous thread to die.
Then call next method.

Your error means that some thread modify your List object, and another thread at the same time iterating it. So thread can’t iterate throught this list when list has changes its content. you should use synchronized block code, some thing like:

List listeners;
...
synchronized(listeners){
    for(Object o : listeners){

    }
}