NullPointerException 空指针异常

所谓空指针异常就是当对象为null时，调用了它的属性或者方法，就会报NullPointerException

package test;

public class Test {
	public String test = "abd";
	
	public void test(){
		System.out.println("test");
	}

	public static void main(String[] args) {
		Test t = null;
		System.out.println(t.test);
		t.test();
	}
}

结果如下：

Exception in thread "main" java.lang.NullPointerException
	at test.Test.main(Test.java:12)