i can't use label in JFrame to display string in another class

who knows ? why i can't use label in JFrame to display string in another java file ?

first file java class (class1):

String [] a = new String(2);
a[0]="ZZz";

second file java class(JFrame) :

i use label. its variabel name is label1
class1 b = new class1();
label.setText(b.a[0]);

when i run my JFrame, the label is blank display. please help.. thanks