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OperatorsTop

Symbols used for mathematical and logical manipulation that are recognized by the compiler are commonly known as operators in Java.

Arithmetic OperatorsTop

We are familiar with most of the arithmetic operators in the table below from everyday life and they generally work in the same way in Java. The arithmetic operators work with all the Java numeric primitive types and can also be applied to the char primitive type.

Relational OperatorsTop

Relational Operators refer to the relationships that values can have to each other. Relational Operators produce a true or false result and are used with control statements such as if and while. Any type can be compared for equality or inequality but only types that support an ordering relationship can be applied for comparison. The table below clarifies this.

Logical OperatorsTop

Logical Operands must be the boolean type and the result of a logical operation is the boolean type and are used with control statements such as if and while. The following table shows all possible combinations and their result.

Assignment OperatorsTop

The single equal sign = is used for assignment in Java and we have been using this throughout the lessons so far. This operator is fairly self explanatory and takes the form variable = expression;. A point to note here is that the type of variable must be compatible with the type of expression.

Shorthand Assignment OperatorsTop

The shorthand assignment operators allow us to write compact code that is is implemented more efficiently.

Bitwise Logical OperatorsTop

The bitwise logical operators perform the same operations as the logical operators discussed in the last lesson but work on a bit-by-bit basis on the integer type. The following table shows all possible combinations for a bit using 0 and 1.

Bitwise Shift OperatorsTop

The bitwise shift operators allow us to shift the bits that make up an integer type to the left or right by a specified amount.

Bitwise Shorthand Assignment OperatorsTop

The bitwise shorthand assignment operators allow us to write compact code that is implemented more efficiently. When using the bitwise shorthand assignment operators there is no need to cast either.

Automatic Type ConversionTop

The following table shows which types can be assigned to which other types, of course we can assign to the same type so these boxes are greyed out.

When using the table use a row for the left assignment and a column for the right assignment. So in the highlighted permutations byte = int won't convert and int = byte will convert.

The new OperatorTop

Object creation is a three step process involving declaration, creation and assignment. We create objects using the new operator which allocates space on the heap for an existing reference variable or one declared at instantiation:

/*
  Examples of class instantiation
*/ 
public class Testinstanceof {

    public static void main (String[] args) {
        Cat moggy = new Cat();    // Declare, create and assign Cat instance
        
        Cat moggy2;   // Declare Cat reference
        moggy2 = new Cat();   // Allocate and assign Cat instance
    } 
}

The instanceof OperatorTop

The instanceof operator can only be used with reference variables. We use the instanceof operator to find out whether an object is of a particular type. Because Java is a strongly typed language, it cares about the type of the variables we declare and try to use. So just be aware when using the instanceof operator to check for a String object, when you have an instance of Monkey that knows nothing about String, you will get a compiler error.

The ? : OperatorTop

The ? : tenary (takes three operands) operator can be used to replace an if....else construct of the following form:

Operator PrecedenceTop

The table below shows the order of precedence that is invoked when Java interprets operator symbols. The list includes the special operators and all the operators are discussed thoroughly in the java section of the site. When using multiple operators in an expression it is always best practice to use parentheses to explicitly state the order of precedence for clarity and readability. The table lists order of precedence from highest to lowest.

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