July 22, 2018
How do I compare strings in java
Introduction
Comparing strings is a very common task in coding. How do we do that in Java ? well there are tons of content in that regard. I compiled the bare minimum that you need in case you are only looking for the syntax.
Take a look…
Syntax Summary
| Comparison type | Syntax | Explanation |
|---|---|---|
| Reference equality | Use == | Check if they are the same object or not ? |
| Value equality | Use .equals() | Do they have the same value |
| Lexicographic equality | Use compareTo | A is less than B and so on |
Let us demonstrate that…
Source code
The following code snippet uses JUnit framework to perform various types of string comparison…
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//Import needed stuff import org.junit.*; import static org.junit.Assert.*; import java.util.*; //Testing class public class Testing { //Constructor public Testing() { System.out.println("In constructor"); } //This method is invoked before //JUnite test case executes @ Before public void setUp() { System.out.println("In setUp"); } //This method is invoked after //JUnit test case is executed @ After public void tearDown() { System.out.println("In tearDown"); } //Test 1 @Test public void testValueEquality() { //Value checking assertTrue(new String("Cisco").equals("Cisco")); //Value checking different syntax assertTrue(Objects.equals(new String("Cisco"), "Cisco")); //Value checking against a null assertFalse(Objects.equals(null, "Cisco")); } //Test 2 @Test public void testObjectEquality() { //Same value but not same objects assertFalse(new String("Cisco") == "Cisco"); //Same value but not same objects assertFalse(new String("Cisco") == new String("Cisco")); //In this case they are internally the same object assertTrue("Cisco" == "Cisco"); } //Test 3 @Test public void testAlphabeticalOrder() { //Lexographic comparison assertTrue(new String("Cisco").compareTo("Apple") > 0); assertTrue(new String("Apple").compareTo("Cisco") < 0); assertTrue(new String("Cisco").compareTo("Cisco") == 0); } } |
Example Output
Compile the code and run the tests as follows…
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javac -cp junit-4.12.jar Testing.java java -cp .:junit-4.12.jar:hamcrest-core-1.3.jar org.junit.runner.JUnitCore Testing |
The output should look like…
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Testing JUnit version 4.12 In constructor .In setUp In tearDown In constructor .In setUp In tearDown In constructor .In setUp In tearDown Time: 0.006 OK (3 tests) |
You can download the source code from here. That is all for today.
Thanks for visiting. For questions and feedback, please use the comments section below
About Author
Mohammed Abualrob
Software Engineer @ Cisco