String Class in Java (Part 2)

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The String Class: (Part 2)

Comparison Methods of String class:

• Example: (equals)

  	/*
  	== cannot be used to check whether two strings has same content or not.
  	== only checks whether the strings are objects of String class or not.
  	To check the content equality, equals() method is used. */
  	class test {
  	public static void main(String ar[]) {
  	String str1 = "Welcome to Java";
  	String str2 = "Welcome to Java";
  	String str3 = new String("Welcome to Java");
  	System.out.println(str1==str2); // true. because str1 and str2 are of variables of same data type ->String
  	System.out.println(str1==str3); // false. because, str1 is a varaible of type String and str3 is an object of class String.
  	System.out.println(str1.equals(str2)); // true. because equals checks the content and the content of str1 and str2 is same.
  	System.out.println(str1.equals(str3)); // true. content of str1 and str3 is the same.
  	}
  	}

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• Example: (equalsIgnoreCase)

  	class test {
  	public static void main(String ar[]) {
  	String str1 = "Java PROGRAMMING";
  	String str2 = "java programming";
  	System.out.println(str1.equalsIgnoreCase(str2)); // true
  	}
  	}

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• Example: (compareTo)

  	class test {
  	public static void main(String ar[]) {
  	String str1 = "A";
  	String str2 = "a";
  	System.out.println(str1.compareTo(str2)); // (65-97 = -32)(A-a)
  	String str3 = "Demo";
  	String str4 = "Eemo";
  	System.out.println(str3.compareTo(str4)); // (68-69 = -1)(D-E)
  	String str5 = "ABCF";
  	String str6 = "ABAI";
  	System.out.println(str5.compareTo(str6));
  	/* check character 1: A-A=0
  	check character 2: B-B=0
  	check character 3: C-A=67-65 =2 (as soon as the score is greater then 0, no further check is done.
  	And the last score is printed. So this prints 2) */
  	}
  	}

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• Example: (compareToIgnoreCase)

  	class test {
  	public static void main(String ar[]) {
  	String str1 = "A";
  	String str2 = "a";
  	System.out.println(str1.compareToIgnoreCase(str2));
  	//removes the case sensitivity and then checks. So this prints 0
  	String str3 = "ABc";
  	String str4 = "abC";
  	System.out.println(str3.compareToIgnoreCase(str4));
  	//removes the case sensitivity and then checks. So this prints 0
  	String str5 = "b";
  	String str6 = "A";
  	System.out.println(str5.compareToIgnoreCase(str6));
  	//removes the case sensitivity of str6 and then checks. Computes: b-a. prints 1
  	String str7 = "A";
  	String str8 = "b";
  	System.out.println(str7.compareToIgnoreCase(str8));
  	//removes the case sensitivity of str8 and then checks. Computes: A-B. prints -1
  	}
  	}

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• Example: (startsWith)

  	class test {
  	public static void main(String ar[]) {
  	String str1 = "Hello!";
  	String str2 = "h";
  	System.out.println(str1.startsWith(str2)); //false. h is lowercase
  	String str3 = "Hello!";
  	String str4 = "H";
  	System.out.println(str3.startsWith(str4)); // true
  	String str5 = "Good Morning!";
  	String str6 = "Good";
  	System.out.println(str5.startsWith(str6)); // true
  	}
  	}

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• Example: (endsWith)

  	class test {
  	public static void main(String ar[]) {
  	String str1 = "Hello!";
  	String str2 = "o";
  	System.out.println(str1.endsWith(str2));
  	//false. 'o' is not the lastmost character
  	String str3 = "Hello!";
  	String str4 = "!";
  	System.out.println(str3.endsWith(str4));
  	// true. '!' is the lastmost character
  	String str5 = "Good Morning!";
  	String str6 = "G!";
  	System.out.println(str5.endsWith(str6));
  	// false. this string ends with g! and not with G!
  	String str7 = "Good Morning!";
  	String str8 = "g!";
  	System.out.println(str7.endsWith(str8)); // true
  	}
  	}

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• Example: (contains)

  	class test {
  	public static void main(String ar[]) {
  	String str1 = "Good Morning!";
  	System.out.println(str1.contains("good")); //false. G is uppercase
  	System.out.println(str1.contains("Good")); //true
  	System.out.println(str1.contains("!")); //true
  	System.out.println(str1.contains("nin")); //true
  	}
  	}

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Click HERE for the Simple Methods of String class.
Click HERE for the Substring Methods of String class.