How to Check Null in Java

A null indicates that a variable doesn't point to any object and holds no value. You can use a basic 'if' statement to check a null in a piece of code. Null is commonly used to denote or verify the non-existence of something. Within that...

Part 1 of 2:

Checking Null in Java

  1. Picture 1 of How to Check Null in Java
    Use '=' to define a variable. A single '=' is used to declare a variable and assign a value to it. You can use this to set a variable to null.
    1. A value of '0' and null are not the same and will behave differently.
    2. variableName = null;
  2. Picture 2 of How to Check Null in Java
    Use '==' to check a variable's value. A '==' is used to check that the two values on either side are equal. If you set a variable to null with '=' then checking that the variable is equal to null would return true.
    1. variableName == null;
    2. You can also use '!=' to check that a value is NOT equal.
  3. Picture 3 of How to Check Null in Java
    Use an 'if' statement to create a condition for the null. The result of the expression will be a boolean (true or false) value. You can use the boolean value as a condition for what the statement does next.
    1. For example, if the value is null, then print text 'object is null'. If '==' does not find the variable to be null, then it will skip the condition or can take a different path.
Object object = null ; if ( object == null ) { System.out.print ( "object is null "); }
Part 2 of 2:

Using a Null Check

  1. Picture 4 of How to Check Null in Java
    Use null as an unknown value. It is common to use null as a default in lieu of any assigned value.
    1. string() means the value is null until it is actually used.
  2. Picture 5 of How to Check Null in Java
    Use null as a condition for ending a process. Returning a null value can be used to trigger the end of a loop or break a process. This is more commonly used to throw an error or exception when something has gone wrong or an undesired condition has been hit.
  3. Picture 6 of How to Check Null in Java
    Use null to indicate an uninitiated state. Similarly, null can be used as flag to show that a process has not yet started or as a condition to mark to be beginning of a process.
    1. For example: do something while object is null or do nothing until an object is NOT null.
synchronized method() { while (method()==null); method().nowCanDoStuff(); }
Update 05 March 2020
nullvalueuseobject

You should read it

Maybe you are interested

Category

System

Mac OS X

Hardware

Game

Tech info

Technology

Science

Life

Application

Electric

Program

Mobile