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Java Built-in Methods

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Java Built-in Methods

Categories of Built in Methods

i) String Methods

ii) Number Methods

iii) Character Methods

iv) Array Methods

etc…

i) String Methods

1) CompareTo() Method

It compares two strings and supports 3-way comparison

Result Criteria for 3-way comparison (Strings)

if string1 = string2 then 0
if string1 > string2 then >0/Positive value
if string1 < string2 then <0 / Negative Value

Comparing Numbers vs. Comparing Strings

Comparing Numbers based on Values

int a =10, b=20;
if (a>b){
Statements
———
——
}

Comparing Strings based on ANSI Character codes

A-Z -(65 to 90)
a-z (97 to 122)
0-9(48 to 57)

Example:

public static void main(String[] args) {
String str1 = “selenium”;
String str2 = “SELENIUM”;
String str3 = “seleniuma”;
String str4 =”selenium”;

System.out.println(str1.compareTo(str2));//>0 / Positive value
System.out.println(str1.compareTo(str3));//<0 / Negative Value
System.out.println(str1.compareTo(str4));//0
}
——————————–
2) equals() Method

Compares two strings and supports 2-way comparison

Result Criteria for 2-way comparison

if string1 = string2 then true
if string1 != string2 then false

Example:

public static void main(String[] args) {
String str1 = “selenium”;
String str2 = “SELENIUM”;
String str3 = “seleniuma”;
String str4 =”selenium”;

System.out.println(str1.equals(str2));//false
System.out.println(str1.equals(str4));//true
System.out.println(str1.equals(“SELENIUM”));//false

System.out.println(str1 == str2);//false
System.out.println(str1 == str4);//true
}
——————————–
3) concat()

It concatenates two strings

public static void main(String[] args) {
String str1 = “Selenium “;
String str2 = “Testing”;

System.out.println(str1.concat(str2));//Selenium Testing
System.out.println(str1 + str2);//Selenium Testing
}
——————————–
4) charAt() method

Returns a Character value by index

Example:

public static void main(String[] args) {
String str1 = “Selenium “;

System.out.println(str1.charAt(4));//n
System.out.println(str1.charAt(40));//Run-time Error
——————————–
5) equalsIgnoreCase()

It compares two strings and supports 2-way comparison

It ignores cases (Upper Case or Lower Case)

Example:

public static void main(String[] args) {
String str1 = “selenium”;
String str2 = “SELENIUM”;
String str3 = “UFT”;

System.out.println(str1.equalsIgnoreCase(str2));//true
System.out.println(str1.equalsIgnoreCase(str3));//false
}
——————————–
6) toUpperCase()

It converts values to Upper case

Example:

public static void main(String[] args) {
String str1 = “selenium”;
String str2 = “SELENIUM”;
String str3 = “SELEnium”;
String str4 = “selenium123”;

System.out.println(str1.toUpperCase());//SELENIUM
System.out.println(str2.toUpperCase());//SELENIUM
System.out.println(str3.toUpperCase());//SELENIUM
System.out.println(str4.toUpperCase());//SELENIUM123
System.out.println(str5.toUpperCase());//S*&^
}
——————————–
7) toLowerCase()

Converts values to Lower case and it ignores Numbers and special characters

Example:

public static void main(String[] args) {
String str1 = “selenium”;
String str2 = “SELENIUM”;
String str3 = “SELEnium”;
String str4 = “selenium123″;
String str5 =”S*&^”;

System.out.println(str1.toLowerCase());//selenium
System.out.println(str2.toLowerCase());//selenium
System.out.println(str3.toLowerCase());//selenium
System.out.println(str4.toLowerCase());//selenium123
System.out.println(str5.toLowerCase());//s*&^
——————————–
8) trim()

Removes spaces from both the sides of a String

Example:

public static void main(String[] args) {
String str1 = ” Selenium “;

System.out.println(str1);
System.out.println(str1.trim());
}
——————————–
9) substring()

It returns sub string based on index

Example:

public static void main(String[] args) {
String str = “Welcome to Selenium Testing”;

System.out.println(str.substring(11));//Selenium Testing
System.out.println(str.substring(20));//Testing
System.out.println(str.substring(11, 19));//Selenium
}
——————————–
10) endsWith()

Ends with specified suffix, and provides Logical (true/false) Result.

Example:

public static void main(String[] args) {
String str = “Welcome to Selenium Testing”;

System.out.println(str.endsWith(“Selenium Testing”));//true
System.out.println(str.endsWith(“Testing”));//true
System.out.println(str.endsWith(“ing”));//true
System.out.println(str.endsWith(“Selenium”));//false
}
——————————–
11) length

Returns length of a String

Example:

public static void main(String[] args) {
String str1 = “Selenium Testing”;
String str2 = “Selenium”;
System.out.println(str1.length());//16
System.out.println(str2.length());//8
}

Java Predefined and Built-in Methods

ii) Number Methods

//Integer Class wraps a value of primitive datatype int in an Object
//An Object of Integer contains a single field whose type is int
——————————–
1) compareTo()

Compares two integers and supports 3-way comparison

Example:

Result Criteria for 3 way Comparison (Integers/Numbers)

if Integer1 = Integer2 then 0
if Integer1 > Integer2 then 1
if Integer1 < Integer2 then -1

public static void main(String[] args) {
int a = 5;
Integer b =a;

System.out.println(b.compareTo(7));//-1
System.out.println(b.compareTo(5));//0
System.out.println(b.compareTo(4));//1
——————————–
2) equals()

Supports 2 way comparison

Example:

public static void main(String[] args) {
int a = 5;
Integer b =a;

System.out.println(b.equals(7));//false
System.out.println(b.equals(5));//true
}
——————————–
3) abs()

Returns absolute value

Example:

public static void main(String[] args) {
double a = 10.456;
double b = 10.786;
double d = -12.34;
int c=7;
int e = -100;

System.out.println(Math.abs(a));//10.456
System.out.println(Math.abs(b));//10.786
System.out.println(Math.abs(c));//7
System.out.println(Math.abs(d));//12.34
System.out.println(Math.abs(e));//100
}
——————————–
4) round()

Rounds the value to nearest integer

Example:
public static void main(String[] args) {
double a = 10.456;
double b = 10.786;
double d = -12.34;
int c=7;
int e = -100;

System.out.println(Math.round(a));//10
System.out.println(Math.round(b));//11
System.out.println(Math.round(c));//7
System.out.println(Math.round(d));//-12
System.out.println(Math.round(e));//-100
}
——————————–
5) min()

Returns minimum value between two numbers

example:

public static void main(String[] args) {
double a = 10.456;
double b = 10.786;
int c =10;
int d= 8;

System.out.println(Math.min(a, b));//10.456
System.out.println(Math.min(c, d));//8
System.out.println(Math.min(5, 4));//4
System.out.println(Math.min(1.234, 2.123));//1.234
System.out.println(Math.min(-10, -8));//-10
System.out.println(Math.min(-1.234, -2.123));//-2.123
}
}
——————————–
6) max()

Returns maximum value between two numbers

Example:

public static void main(String[] args) {
double a = 10.456;
double b = 10.786;
int c =10;
int d= 8;

System.out.println(Math.max(a, b));//10.786
System.out.println(Math.max(c, d));//10
System.out.println(Math.max(5, 4));//5
System.out.println(Math.max(1.234, 2.123));//2.123
System.out.println(Math.max(-10, -8));//-8
System.out.println(Math.max(-1.234, -2.123));//-1.234
}
——————————–
7) random()

Generates a Random Number

Example:

public static void main(String[] args) {
System.out.println(Math.random());//
}

iii) Character Methods

// The Character class wraps a value of primitive data type char in an object

1) isLetter()

Checks if the value is Alpha byte or not? and returns Logical (true/false) result.

public static void main(String[] args) {
char a =’A’;
char b =’a’;
char c =’1′;
char d = ‘*’;

System.out.println(Character.isLetter(a));//true
System.out.println(Character.isLetter(b));//true
System.out.println(Character.isLetter(c));//false
System.out.println(Character.isLetter(d));//false
System.out.println(Character.isLetter(‘Z’));//true
System.out.println(Character.isLetter(‘7’));//false
}
——————————–
2) isAlphabetic()

Checks if the value is Alpha byte or not? and returns Logical (true/false) result.

Example:

public static void main(String[] args) {
char a =’A’;
char b =’a’;
char c =’1′;
char d = ‘*’;

System.out.println(Character.isAlphabetic(a));//true
System.out.println(Character.isAlphabetic(b));//true
System.out.println(Character.isAlphabetic(c));//false
System.out.println(Character.isAlphabetic(d));//false
System.out.println(Character.isAlphabetic(‘Z’));//true
System.out.println(Character.isAlphabetic(‘7’));//false
}
——————————–
Assignment:

What is the difference between isLetter and isAlphabetic methods.
——————————–
3) isDigit

Checks if the value is Number or not?

public static void main(String[] args) {
char a =’A’;
char b =’1′;

System.out.println(Character.isDigit(a));//false
System.out.println(Character.isDigit(b));//true
System.out.println(Character.isDigit(‘B’));//false
System.out.println(Character.isDigit(‘9’));//true
}
——————————–
4) isUpperCase()

Checks if the value is Upper Case or not?

5) isLowerCase

Checks if the value is Lower Case or not?

Examples:

public static void main(String[] args) {
char a =’A’;
char b =’a’;
char c =’1′;

System.out.println(Character.isUpperCase(a));//true
System.out.println(Character.isUpperCase(b));//false
System.out.println(Character.isUpperCase(c));//false

System.out.println(Character.isLowerCase(a));//false
System.out.println(Character.isLowerCase(b));//true
}

iv) Array Methods

1) length()

It returns length of an Array

Example:

public static void main(String[] args) {
int [] array1 = {10, 20, 30, 40, 5};
System.out.println(array1.length);//5
}
——————————–
2) toString()

Prints an Array

public class Class1 {

public static void main(String[] args) {
String [] array1 = {“Selenium”, “UFT”, “RFT”, “SilkTest”};

String str = Arrays.toString(array1);
System.out.println(str); //[Selenium, UFT, RFT, SilkTest]

for (int i=0; i < array1.length; i++){
System.out.println(array1[i]);
}
——————————–
3) contains()

Checks if the Array contains certain value or not?, returns boolean result.

Example:

public static void main(String[] args) {
String [] array1 = {“Selenium”, “UFT”, “RFT”, “SilkTest”};
boolean a = Arrays.asList(array1).contains(“UFT”);//
System.out.println(a);//true

System.out.println(Arrays.asList(array1).contains(“Selenium”));//true
System.out.println(Arrays.asList(array1).contains(“Java”));//false
}
——————————–
Method Syntax:

object.method();
class.method();
Class/object.property.method();
etc…
———————-

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G C Reddy

G C Reddy, Working as a Software Testing Trainer in Hyderabad, India.

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