final修饰符如何在java中使用

package objectStudy;public class FinalInstanceVaribaleTest { final int var1 = 1;//定义final实例变量时指定初始值。 final int var2; final int var3;  //在非静态初始化块中为final实例变量指定初始值。 {  var2 = 2; }  // 在构造方法中为final实例变量指定初始值。 public FinalInstanceVaribaleTest() {  this.var3 = 3; }  public static void main(String[] args) {  FinalInstanceVaribaleTest finalInstanceVaribaleTest = new FinalInstanceVaribaleTest();  System.out.println(finalInstanceVaribaleTest.var1);  System.out.println(finalInstanceVaribaleTest.var2);  System.out.println(finalInstanceVaribaleTest.var3); }}