Wrapper Classes

• Character Documentation

• Integer Documentation

• Double Documentation

Character

The Character class serves as a wrapper for the primitive char type. It provides several convenient methods for working with and manipulating characters.

Methods

There are many methods available to the Character class. These will likely be the most useful to you.

• isAlphabetic(int codePoint)

The isAlphabetic method determines if the specified character is an alphabet. It accepts an int parameter, which is a Unicode code point.

char alpha = 'A';
char numeric = '3';

Character.isAlphabetic(alpha);      // true
Character.isAlphabetic(numeric);    // false

There is a variation of this method that accepts a char as a parameter.

• isDigit(int codePoint)

The isDigit methods determines if the specified character is a digit. It accepts an int parameter, which is a Unicode code point.

char letter = 'A';
char number = '7';

Character.isDigit(letter);    // false
Character.isDigit(number);    // true

There is a variation of this method that accepts a char as a parameter.

• isLetter(int codePoint)

The isLetter method determines if the specified character is a letter. It accepts an int parameter, which is a Unicode code point.

char letter = 'A';
char number = '7';

Character.isLetter(letter);    // true
Character.isLetter(number);    // false

There is a variation of this method that accepts a char as a parameter.

• isLetterOrDigit(int codePoint)

The isLetterOrDigit method determines if the specified character is either a letter or a digit. It accepts an int parameter, which is a Unicode code point.

char letter = 'A';
char digit = '7';
char special = '$';

Character.isLetterOrDigit(letter);     // true
Character.isLetterOrDigit(digit);      // true
Character.isLetterOrDigit(special);    // false

There is a variation of this method that accepts a char as a parameter.

• isLowerCase(int codePoint)

The isLowerCase method determines if the specified character is a lowercase character. It accepts an int parameter, which is a Unicode code point.

char lower = 'a';
char upper = 'A';

Character.isLowerCase(lower);    // true
Character.isLowerCase(upper);    // false

There is a variation of this method that accepts a char as a parameter.

• isSpaceChar(int codePoint)

The isSpaceChar method determines if the specified character is a space character. It accepts an int parameter, which is a Unicode code point.

char space = ' ';
char newline = '\n';
char tab = '\t';

Character.isSpaceChar(space);      // true
Character.isSpaceChar(newline);    // false
Character.isSpaceChar(tab);        // false

There is a variation of this method that accepts a char as a parameter.

• isUpperCase(int codePoint)

The isUpperCase method determines if the specified character is an uppercase character. It accepts an int parameter, which is a Unicode code point.

char lower = 'a';
char upper = 'A';

Character.isLowerCase(lower);    // false
Character.isLowerCase(upper);    // true

There is a variation of this method that accepts a char as a parameter.

• isWhitespace(int codePoint)

The isWhitespace method determines if the specified character is a whitespace character (by Java's definition of whitespace). It accepts an int parameter, which is a Unicode code point.

char space = ' ';
char newline = '\n';
char tab = '\t';

Character.isWhiteSpace(space);      // true
Character.isWhiteSpace(newline);    // true
Character.isWhiteSpace(tab);        // true

There is a variation of this method that accepts a char as a parameter.

You can check out all of the available methods and fields in the full documentation.

Integer

The Integer class serves as a wrapper for the primitive type int. It provides several convenient methods and constants for working with integers, and converting them to and from Strings.

Fields

There are two fields you should be familiar with, though more are available.

• MAX_VALUE

The MAX_VALUE field represents the largest value that an int can have.

int largestValue = Integer.MAX_VALUE;

• MIN_VALUE

The MIN_VALUE field represents the smallest value that an int can have.

int smallestValue = Integer.MIN_VALUE;

Methods

While there are many methods, here are the two that you'll find yourself using most frequently.

• toString(int i)

The toString method returns the String representation of the integer value.

Integer.toString(7);           // "7" (static call)

• valueOf(String s)

The valueOf method returns an Integer object of the specified String.

Integer i = Integer.valueOf("12");    // wraps int 12

You can check out all of the available methods and fields in the full documentation.

Double

The Double class serves as a wrapper for the primitive type double. It provides several convenient methods and constants for working with floating-point values, and converting them to and from Strings.

Fields

There are seven fields you should be familiar with, though more are available.

• MAX_EXPONENT

The MAX_EXPONENT field represents the maximum exponent a finite double can have.

int maxExponent = Double.MAX_EXPONENT;

• MAX_VALUE

The MAX_VALUE field represents the largest value that a double can have.

double max = Double.MAX_VALUE;

• MIN_VALUE

The MIN_VALUE field represents the smallest value that a double can have.

double min = Double.MIN_VALUE;

• NaN

The NaN field represents not a number, which can be the result of certain undefined arithmetic operations.

double quotient = 0.0 / 0;             // Double.NaN

• NEGATIVE_INFINITY

The NEGATIVE_INFINITY field represents -∞, which can be the result of certain undefined arithmetic operations.

double negativeInfinity = -1 / 0.0;    // Double.NEGATIVE_INFINITY

• POSITIVE_INFINITY

The POSITIVE_INFINITY field represents ∞, which can be the result of certain undefined arithmetic operations.

double positiveInfinity = 1 / 0.0;     // Double.POSITIVE_INFINITY

Methods

While there are many methods, here are the two that you'll find yourself using most frequently.

• isFinite(double d)

The isFinite method returns true if the specified value is a finite floating-point value. It returns false otherwise, including NaN and infinity values.

boolean a = Double.isFinite(7.32);         // true
boolean b = Double.isFinite(1 / 0.0);      // false

• isInfinite(double v)

The isInfinite method returns true if the specified value is infinitely large. It returns false otherwise.

boolean a = Double.isInfinite(7.32);       // false
boolean b = Double.isInfinite(1 / 0.0);    // true

• isNaN(double v)

The isNaN method returns true if the specified value is not a number.

boolean a = Double.isNaN(0.0 / 0);         // true

• toString(double d)

The toString method returns the String representation of the double value.

Double.toString(7.0);           // "7.0" (static call)

• valueOf(String s)

The valueOf method returns a Double object of the specified String.

Double d = Double.valueOf("12.0");    // wraps double 12.0

You can check out all of the available methods and fields in the full documentation.