java之对象引用static变量-优快云博客

本文链接：https://blog.youkuaiyun.com/abc357024/article/details/83770118

本文探讨了Java中静态变量与实例变量的区别，通过不同代码示例展示了如何访问静态变量及访问null对象的实例变量时发生的NullPointerException。

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如下面代码

Java代码
public class Test
{
public static int a = 2;

public static void main(String[] args)
{
Test t = new Test();

t = null;

System.out.println(t.a);
}
}

public class Test
{
public static int a = 2;

public static void main(String[] args)
{
Test t = new Test();

t = null;

System.out.println(t.a);
}
}

输出为：

Java代码
2

2

下面的代码

Java代码
public class Test
{
public static int a = 2;
public int b = 3;

public static void main(String[] args)
{
Test t = new Test();

t = null;

System.out.println(t.a);
System.out.println(t.b);
}
}

public class Test
{
public static int a = 2;
public int b = 3;

public static void main(String[] args)
{
Test t = new Test();

t = null;

System.out.println(t.a);
System.out.println(t.b);
}
}

输出为：

Java代码
2
Exception in thread "main" java.lang.NullPointerException

2
Exception in thread "main" java.lang.NullPointerException

再看下面的代码：

Java代码
public class Test
{
public int a = 3;
public static int b = 2;

public static void main(String[] args)
{
Test t = new Test();

t = null;

System.out.println(t.a);
System.out.println(t.b);
}
}

public class Test
{
public int a = 3;
public static int b = 2;

public static void main(String[] args)
{
Test t = new Test();

t = null;

System.out.println(t.a);
System.out.println(t.b);
}
}

输出为：

Java代码
Exception in thread "main" java.lang.NullPointerException

Exception in thread "main" java.lang.NullPointerException