[Chapter 4] 4.11 Boolean Operators
Author: Mark Grand
Date: Thu Jul 31 13:10:36 1997

#

| Chapter 4 Expressions |

## 4.11 Boolean Operators

The Boolean operators in Java are used for conditional AND (`&&`) and conditional OR (`||`) operations. These operators have different precedence; the `&&` operator has the higher precedence and `||` the lower precedence. Both of the operators are evaluated from left to right.

The unary operator `!` provides a Boolean negation operation.

References Boolean Negation Operator !; Order of Operations

### Boolean AND Operator &&

The conditional AND operator `&&` produces a pure `boolean` value that is the conditional AND of its operands. The `&&` operator may appear in a conditional AND expression:

The conditional AND operator is evaluated from left to right. The operator never throws an exception.

Here is a code example that shows the use of the conditional AND operator:

    public final short readShort() throws IOException {
        int ch1, ch2;
        if ((ch1 = in.read()) >= 0 && (ch2 = in.read()) >= 0)
            return (short)((ch1 << 8) + ch2);
        throw new EOFException();
    }

The operands of the conditional AND operator must both be of type `boolean`, or a compile-time error occurs.

The operands of the conditional AND operator are evaluated in a different way from the operands for most other operators in Java. Most other operators evaluate all of their operands before performing their operation; the conditional AND operator does not necessarily evaluate both of its operands.

As with all binary operators, the left operand of `&&` is evaluated first. If the left operand evaluates to `true`, the conditional AND operator evaluates its right operand and produces a pure value that has the same value as its right operand. However, if the left operand evaluates to `false`, the right operand is not evaluated and the operator produces the pure value `false`.

In the above example, the expression `(ch2 = in.read())` is evaluated only if the expression `(ch1 = in.read())` produces a value that is greater than or equal to zero.

References Bitwise/Logical AND Operator &; Boolean Type; Bitwise/Logical Inclusive OR Operator |; Order of Operations

### Boolean OR Operator ||

The conditional OR operator `||` produces a pure `boolean` value that is the conditional OR of its operands. The `||` operator may appear in a conditional OR expression:

The conditional OR operator is evaluated from left to right. The operator never throws an exception.

Here is a code example that shows the use of the conditional OR operator:

    public final short readShort() throws IOException {
        int ch1, ch2;
        if ((ch1 = in.read()) < 0 || (ch2 = in.read()) < 0)
            throw new EOFException();
        return (short)((ch1 << 8) + ch2);
    }

The operands of the conditional OR operator must both be of type `boolean`, or a compile-time error occurs.

The operands of the conditional OR operator are evaluated in a different way from the operands for most other operators in Java. Most other operators evaluate all of their operands before performing their operation; the conditional OR operator does not necessarily evaluate both of its operands.

As with all binary operators, the left operand of `||` is evaluated first. If the left operand evaluates to `false`, the conditional OR operator evaluates its right operand and produces a pure value that has the same value as its right operand. However, if the left operand evaluates to `true`, the right operand is not evaluated and the operator produces the pure value `true`.

References Bitwise/Logical Inclusive OR Operator |; Boolean Type; Boolean AND Operator &&; Order of Operations

Bitwise/Logical Operators |  | Conditional Operator