Java 引用变量

原文： https://javabeginnerstutorial.com/core-java-tutorial/java-reference-variable/

引用变量用于引用对象。 它们以无法更改的特定类型声明。

引用变量的类型

  • 静态变量
  • 实例变量
  • 方法参数
  • 局部变量

静态变量示例

  1. class test {
  2.     //below variable is static variable means it is class level variable
  3.     static int i;
  5.     public static void main(String[] args) {
  6.         // As i is an static variable it can be accessed directly without using any object
  7.         System.out.println("Value before calling method1: " + i);
  8.         test t1 = new test();
  9.         t1.method1();
  10.         System.out.println("Value after calling method1: " + i);
  11.         t1.method2();
  12.         System.out.println("Value after calling method2: " + i);
  13.     }
  15.     void method1() {
  16.         i++;
  17.     }
  19.     void method2() {
  20.         i++;
  21.     }
  23. }

实例/局部/方法参数示例

  1. class MPE {
  2.     // Instance Variable
  3.     int i;
  5.     public static void main(String[] args) {
  6.         /*
  7.          * Here i is an Instance variable.
  8.          */
  9.         test t1 = new test();
  10.         System.out.println("Value before calling method1: " + t1.i);
  12.     }
  14.     /*
  15.      * Here j is a method parameter. And k is a local variable.
  16.      * 
  17.      * Note**: Local variables life is only till the end of method
  18.      */
  19.     void method1(int j) {
  20.         int k;
  21.         i = j;
  22.         /*
  23.          * Local Variable(k)'s life ends once execution for this method
  24.          * completes. As k is local is variable it needs to be initialized 
  25.          * before we can use it. But as it is not getting used here, it can stay here without initializing
  26.          */
  28.     }
  29. }