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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 context, it can be used as a condition to start or stop other processes within the code.[1]
Steps
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![Step 1 Use “=” to define a variable.]()
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.- A value of “0” and null are not the same and will behave differently.
variableName = null;
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![Step 2 Use “==” to check a variable’s value.]()
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.variableName == null;- You can also use “!=” to check that a value is NOT equal.
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![Step 3 Use an “if” statement to create a condition for the null.]()
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.- 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 "); }
- 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.
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![Step 1 Use null as an unknown value.]()
Use null as an unknown value. It is common to use null as a default in lieu of any assigned value.-
string()means the value is null until it is actually used.
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![Step 2 Use null as a condition for ending a process.]()
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. -
![Step 3 Use null to indicate an uninitiated state.]()
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.- For example: do something while object is null or do nothing until an object is NOT null.
synchronized method() { while (method()==null); method().nowCanDoStuff(); }
- For example: do something while object is null or do nothing until an object is NOT null.
Expert Q&A
Tips
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Some consider heavy use of nulls a poor practice in object oriented programming, where values should always be pointed to objects.[2] [3]Thanks
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