String comparison in Java:
We can compare two given strings on the basis of content and reference.
It is used in authentication (by equals() method), sorting (by compareTo()
method), reference matching (by == operator) etc.
There are three ways to compare String objects:
1)By equals() method
2)By = = operator
3)By compareTo() method
1) By equals() method:
equals() method compares the original content of the string.It compares values
of string for equality.String class provides two methods:
public boolean equals(Object another){} compares this string to the specified
object.
public boolean equalsIgnoreCase(String another){} compares this String to
another String, ignoring case.
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class stringtest{ public static void main(String args[]){ String s1="deepak"; String s2="deepak"; String s3=new String("deepak"); String s4="Saurav"; System.out.println(s1.equals(s2));//true System.out.println(s1.equals(s3));//true System.out.println(s1.equals(s4));//false } } |
Example of equalsIgnoreCase(String) method
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class stringtest2{ public static void main(String args[]){ String s1="deepak"; String s2="DEEPAK"; System.out.println(s1.equals(s2));//false System.out.println(s1.equalsIgnoreCase(s3));//true } } |
2) By == operator
The = = operator compares references not values.
Example of == operator
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class Teststring{ public static void main(String args[]){ String s1="deepak"; String s2="deepak"; String s3=new String("deepak"); System.out.println(s1==s2);//true (because both refer to same instance) System.out.println(s1==s3);//false(because s3 refers to instance created in nonpool) } } |
3) By compareTo() method:
compareTo() method compares values and returns an int which tells if the values
compare less than, equal, or greater than.
Suppose s1 and s2 are two string variables.If:
s1 == s2 :0
s1 > s2 :positive value
s1 < s2 :negative value
Example of compareTo() method:
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class Testcomparison{ public static void main(String args[]){ String s1="deepak"; String s2="deepak"; String s3="Rajan"; System.out.println(s1.compareTo(s2));//0 System.out.println(s1.compareTo(s3));//1(because s1>s3) System.out.println(s3.compareTo(s1));//-1(because s3 < s1 ) } } |