NumberFormatException with calculator

Question

I'm making a calculator, and I'm getting a NumberFormatException.

This is the code for my method:

String[] parts = text.getText().split(" + ", 2);
temporary[0] = Integer.parseInt(parts[0]);
temporary[1] = Integer.parseInt(parts[0]);
answer = temporary[0] + temporary[1];

This is the code for my class:

public int answer = 0;
public int[] temporary = {0, 0};

I'm getting the NFE on this line:

temporary[0] = Integer.parseInt(parts[0]);

Any ideas why?

This is my stacktrace:

Exception in thread "AWT-EventQueue-0" java.lang.NumberFormatException: For input string: "8 + 9"
at java.lang.NumberFormatException.forInputString(Unknown Source)
at java.lang.Integer.parseInt(Unknown Source)
at java.lang.Integer.parseInt(Unknown Source)
at main.Calculator.actionPerformed(Calculator.java:123)
at javax.swing.AbstractButton.fireActionPerformed(Unknown Source)
at javax.swing.AbstractButton$Handler.actionPerformed(Unknown Source)
at javax.swing.DefaultButtonModel.fireActionPerformed(Unknown Source)
at javax.swing.DefaultButtonModel.setPressed(Unknown Source)
at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(Unknown Source)
at java.awt.Component.processMouseEvent(Unknown Source)
at javax.swing.JComponent.processMouseEvent(Unknown Source)
at java.awt.Component.processEvent(Unknown Source)
at java.awt.Container.processEvent(Unknown Source)
at java.awt.Component.dispatchEventImpl(Unknown Source)
at java.awt.Container.dispatchEventImpl(Unknown Source)
at java.awt.Component.dispatchEvent(Unknown Source)
at java.awt.LightweightDispatcher.retargetMouseEvent(Unknown Source)
at java.awt.LightweightDispatcher.processMouseEvent(Unknown Source)
at java.awt.LightweightDispatcher.dispatchEvent(Unknown Source)
at java.awt.Container.dispatchEventImpl(Unknown Source)
at java.awt.Window.dispatchEventImpl(Unknown Source)
at java.awt.Component.dispatchEvent(Unknown Source)
at java.awt.EventQueue.dispatchEventImpl(Unknown Source)
at java.awt.EventQueue.access$200(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
at java.awt.EventQueue$4.run(Unknown Source)
at java.awt.EventQueue$4.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
at java.awt.EventQueue.dispatchEvent(Unknown Source)
at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.run(Unknown Source)

Answer 1

split uses regex so split(" + ") will try to split on two or more continues spaces and since your String probably don't have such spaces it will not be split so parts[0] will hold entire original String. Because of that your code will try to parse something like

Integer.parseInt("123 + 321")` 

which throws NumberFormatException because it is not correct integer this method can parse. Try escaping + in split. You can also make spaces optional.

Try with

String[] parts = text.getText().split("\\s*\\+\\s*", 2);

---

Also note that you are trying to parse parts[0] twice. Change your

temporary[1] = Integer.parseInt(parts[0]);

to

temporary[1] = Integer.parseInt(parts[1]);