What is the problem this code? Why this class open two times ?

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Java

netbeans

My application is firstly open class2 (my main page). When I was click the button in class2 = open class1 (but class2 open background). Then my question = click the button in class1 to sent some text to textfield in class2(this is second class2). And the sending text go there (records are mixed). I don't want to second one. How can I fix this. I am so sory my English maybe I have to put project competely. Thank you for helping..

This is my project link:(I could explain it better.)
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This is class1.java ;

public void sent(class2 theOtherClassInstance) {
if (jCheckBox1.isSelected()) {
theOtherClassInstance.jTextField1.setText("sent this text"); // "jtextfield1" in class2
}
}

private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) { 
class2 theOtherClassInstance = new class2();
theOtherClassInstance.setVisible(true);
sent(theOtherClassInstance);
this.setVisible(false);
}