Posted by: lrrp | June 29, 2015

What happens When System.out.println(null)?

    • Compilation Error -This is because you can pass an Object or a String or char[]. Since null can fit in both, the compiler doesn’t know which method to use, leading to compile error.
  • Method Overloading:
    1.public void prinltln(String str) { }
    2.public void prinltln(char[] ch){ }
    3.public void prinltln(Object ch){
  •  It seems the call System.out.print(null) is ambiguous to compiler because print(null) here will find the two best specific matches i.e. print(String) and print(char[]) . So compiler is unable to determine which method to call here .
  • Compilation Error:
    System.out.println(null)
  • Compile Fine:
    System.out.println((String)null);//null
    System.out.println((char[])null);
    System.out.println((Object)null);//null
  • It’s the compiler type-checking the parameters of the method call.
  • But here we need to know one more thing  System.out.println((char[])null); will compile fine but at run time will throw runtime exception.

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