java self assignment

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Why is this an issue?

There is no reason to re-assign a variable to itself. Either this statement is redundant and should be removed, or the re-assignment is a mistake and some other value or variable was intended for the assignment instead.

Noncompliant code example

Compliant solution.

• CERT, MSC12-C. - Detect and remove code that has no effect or is never executed

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Self assignment ¶

Click to see the query in the CodeQL repository

Assigning a variable to itself does not have any effect. Therefore, such an assignment is either completely unnecessary, or it indicates a typo or a similar mistake.

Recommendation ¶

If the assignment is unnecessary, remove it. If the assignment indicates a typo or a similar mistake, correct the mistake.

The following example shows part of a method that is intended to make a copy of an existing MotionEvent without preserving its history. On line 8, o.mFlags is assigned to itself. Given that the statement is surrounded by statements that transfer information from the fields of o to the fields of the new event, ev , the statement is clearly a mistake. To correct this, the mFlags value should be assigned to ev.mFlags instead, as shown in the corrected method.

References ¶

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Operators constitute the basic building block of any programming language. Java too provides many types of operators which can be used according to the need to perform various calculations and functions, be it logical, arithmetic, relational, etc. They are classified based on the functionality they provide.

Types of Operators: 

• Arithmetic Operators
• Unary Operators
• Assignment Operator
• Relational Operators
• Logical Operators
• Ternary Operator
• Bitwise Operators
• Shift Operators

This article explains all that one needs to know regarding Assignment Operators. 

Assignment Operators

These operators are used to assign values to a variable. The left side operand of the assignment operator is a variable, and the right side operand of the assignment operator is a value. The value on the right side must be of the same data type of the operand on the left side. Otherwise, the compiler will raise an error. This means that the assignment operators have right to left associativity, i.e., the value given on the right-hand side of the operator is assigned to the variable on the left. Therefore, the right-hand side value must be declared before using it or should be a constant. The general format of the assignment operator is, 

Types of Assignment Operators in Java

The Assignment Operator is generally of two types. They are:

1. Simple Assignment Operator: The Simple Assignment Operator is used with the “=” sign where the left side consists of the operand and the right side consists of a value. The value of the right side must be of the same data type that has been defined on the left side.

2. Compound Assignment Operator: The Compound Operator is used where +,-,*, and / is used along with the = operator.

Let’s look at each of the assignment operators and how they operate: 

1. (=) operator: 

This is the most straightforward assignment operator, which is used to assign the value on the right to the variable on the left. This is the basic definition of an assignment operator and how it functions. 

Syntax:  

Example:  

2. (+=) operator: 

This operator is a compound of ‘+’ and ‘=’ operators. It operates by adding the current value of the variable on the left to the value on the right and then assigning the result to the operand on the left. 

Note: The compound assignment operator in Java performs implicit type casting. Let’s consider a scenario where x is an int variable with a value of 5. int x = 5; If you want to add the double value 4.5 to the integer variable x and print its value, there are two methods to achieve this: Method 1: x = x + 4.5 Method 2: x += 4.5 As per the previous example, you might think both of them are equal. But in reality, Method 1 will throw a runtime error stating the “i ncompatible types: possible lossy conversion from double to int “, Method 2 will run without any error and prints 9 as output.

Reason for the Above Calculation

Method 1 will result in a runtime error stating “incompatible types: possible lossy conversion from double to int.” The reason is that the addition of an int and a double results in a double value. Assigning this double value back to the int variable x requires an explicit type casting because it may result in a loss of precision. Without the explicit cast, the compiler throws an error. Method 2 will run without any error and print the value 9 as output. The compound assignment operator += performs an implicit type conversion, also known as an automatic narrowing primitive conversion from double to int . It is equivalent to x = (int) (x + 4.5) , where the result of the addition is explicitly cast to an int . The fractional part of the double value is truncated, and the resulting int value is assigned back to x . It is advisable to use Method 2 ( x += 4.5 ) to avoid runtime errors and to obtain the desired output.

Same automatic narrowing primitive conversion is applicable for other compound assignment operators as well, including -= , *= , /= , and %= .

3. (-=) operator: 

This operator is a compound of ‘-‘ and ‘=’ operators. It operates by subtracting the variable’s value on the right from the current value of the variable on the left and then assigning the result to the operand on the left. 

4. (*=) operator:

 This operator is a compound of ‘*’ and ‘=’ operators. It operates by multiplying the current value of the variable on the left to the value on the right and then assigning the result to the operand on the left. 

5. (/=) operator: 

This operator is a compound of ‘/’ and ‘=’ operators. It operates by dividing the current value of the variable on the left by the value on the right and then assigning the quotient to the operand on the left. 

6. (%=) operator: 

This operator is a compound of ‘%’ and ‘=’ operators. It operates by dividing the current value of the variable on the left by the value on the right and then assigning the remainder to the operand on the left. 

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All about java assignment operators.

Like every other programming language, Java language also provides a feature called Operators. There are a few types of Operators exist in Java. In this java tutorial, we will focus our learning on Assignment operators.

Assignment Operators exist for assigning a value to a variable in Java. The right side of the operator will be a value and the left side will be the variable that we created. So a general syntax would be as follows:

Simple Assignment Operator:

+= Assignment Operator:

-= assignment operator:, *= assignment operator:, /= assignment operator:.

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Java Programming Self-Assessment

Newly admitted Computer Science and Systems students begin their programming coursework in either of three courses, depending on experience and skills:

• TCSS 142, Intro. to Object-Oriented Programming - For students with minimal programming experience or who feel they would benefit from a review of basic concepts
• TCSS 143, Foundations of Object-Oriented Programming - for students who have taken the equivalent of TCSS 142  and are confident in their mastery of the course material
• TCSS 305, Programming Practicum - For students who have taken the equivalent of TCSS 143  and are confident in their understanding of object-oriented programming concepts and techniques

Not sure where to start? Take our assessment.

It is important for you to know the level of knowledge required to progress to the next programming course. To help you make an informed decision about where to begin, the following self-assessment exams have been provided. If you have taken the equivalent of TCSS 142, you should take the TCSS 143 assessment test to verify your mastery of the required prerequisite knowledge. Likewise, if you have taken the equivalent of TCSS 143, you should take the TCSS 305 assessment test.

Please make sure to take your time and allow yourself up to one hour. This assessment will only be of value if you make an honest effort.

• TCSS 143 Self-Assessment Test
• TCSS 305 Self-Assessment Test

To find out how well you performed, download the answer key:

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• TCSS 305 answer key

Follow up with an advisor

After you take the exam, you should meet with an academic adviser to discuss the results. Contact SET advising  to make an appointment.

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