public class Test {
public static void main(String[] args) {
String s = null;
String s1 = null;
Integer i = null;
Integer i1 = null;
System.out.println(s+i);
System.out.println(i+s);
System.out.println(s+s1);
try {
System.out.println(i+i1);
} catch (NullPointerException np) {
System.out.print("NullPointerException");
}
}
}
问题很简单——为什么我NullPointerException
只在最后一行收到一个?