{"id":4077,"date":"2018-04-20T08:51:28","date_gmt":"2018-04-20T12:51:28","guid":{"rendered":"http:\/\/springframework.guru\/?p=4077"},"modified":"2019-06-16T03:17:51","modified_gmt":"2019-06-16T07:17:51","slug":"java-string-to-int","status":"publish","type":"post","link":"https:\/\/springframework.guru\/java-string-to-int\/","title":{"rendered":"Java String to Int"},"content":{"rendered":"

A common requirement while programming in Java is to convert String<\/code> to int<\/code>. UI inputs in Web-based HTML, JSP, or Thymeleaf templates are transferred to backend Java applications as strings. It is the application developer\u2019s responsibility to perform any String<\/code> to int<\/code> conversions to fulfill business logic, such as calculating discounts, storing age, and so on.<\/p>\n

In this post, I’ll discuss how to convert String in Java to int.<\/p>\n

The Integer.parseInt Method<\/h2>\n

The Integer.parseInt()<\/code> method takes as input a String<\/code> and returns an int<\/code> value.<\/p>\n

The code to use this method is.<\/p>\n

public int convertWithParseInt(String str){\r\n    int num = Integer.parseInt(str);\r\n    return num;\r\n}\r\n<\/pre>\n
Here is the test code in JUnit<\/a>.<\/p>\n
package springframework.guru;\r\n\r\nimport org.junit.After;\r\nimport org.junit.Before;\r\nimport org.junit.Test;\r\nimport static org.junit.Assert.assertEquals;\r\n\r\npublic class StringToIntConverterTest {\r\n\r\n    private StringToIntConverter stringToIntConverter;\r\n    String str;\r\n\r\n    @Before\r\n    public void setUp(){\r\n        str = \"369\";\r\n        stringToIntConverter=new StringToIntConverter();\r\n    }\r\n    @After\r\n   public void tearDown(){\r\n        str = null;\r\n    }\r\n\r\n    @Test\r\n    public void convertWithParseInt() {\r\n        int val= stringToIntConverter.convertWithParseInt(str);\r\n        System.out.println(val);\r\n        assertEquals(val, 369);\r\n\r\n    }\r\n\r\n}\r\n<\/pre>\n
The output on running the test in InteliJ is this.<\/p>\n
\"Test<\/a><\/p>\n
The Integer<\/code> class also provides an overloaded parseInt()<\/code> method that additionally accepts the radix<\/a> (base) to be used while parsing.<\/p>\n
Here is the code to use the overloaded method..<\/p>\n
public int convertWithParseIntWithRadix(String str, int radix){\r\n    int num = Integer.parseInt(str, radix);\r\n    return num;\r\n}\r\n<\/pre>\n
Here is the test code.<\/p>\n
@Test\r\npublic void convertWithParseIntWithRadix() {\r\n    int val= stringToIntConverter.convertWithParseIntWithRadix(\"1010110\", 2);\r\n    System.out.println(val);\r\n    assertEquals(val, 86);\r\n}<\/pre>\n
The output on running the test in InteliJ is this.
\n\"Java<\/a><\/p>\n
Handling Parsing Exception<\/h2>\n
The parseInt()<\/code> method throws a NumberFormatException<\/code> if the String<\/code> does not contain a parsable int<\/code>.<\/p>\n
Here is a sample code to handle the NumberFormatException<\/code> gracefully.<\/p>\n
public static final int DEFAULT_DEFAULT_PARSED_INT = 0;\r\npublic int tryConvertWithParseInt(String str){\r\n    try {\r\n        int number = Integer.parseInt(str);\r\n        return number;\r\n    }\r\n    catch(NumberFormatException e){\r\n        return DEFAULT_DEFAULT_PARSED_INT;\r\n    }\r\n}<\/pre>\n
This code returns a default int<\/code> value whenever a NumberFormatException<\/code> is thrown by the parseInt()<\/code> method.<\/p>\n
Here is the JUnit test code.<\/p>\n
@Test\r\npublic void tryConvertWithParseInt() {\r\n    int valA = stringToIntConverter.tryConvertWithParseInt(str);\r\n    int valB = stringToIntConverter.tryConvertWithParseInt(\"abc\");\r\n    System.out.println(valA);\r\n    assertEquals(valA, 369);\r\n    System.out.println(valB);\r\n    assertEquals(valB, 0);\r\n\r\n}<\/pre>\n
The test output is this.
\n\"Java<\/a><\/p>\n
The Integer.valueOf Method<\/h2>\n
The Integer class also comes with the static valueOf()<\/code> method to convert String<\/code> to int<\/code>. The valueOf()<\/code> method interprets the String<\/code> exactly as if it were given to parseInt()<\/code>. In fact, the valueOf()<\/code> method internally uses the parseInt()<\/code> method.<\/p>\n
However, valueOf()<\/code> returns a new Integer<\/code> object whereas parseInt()<\/code> returns a primitive int<\/code>.<\/p>\n
The code to parse String<\/code> using the valueOf()<\/code> method is this.<\/p>\n
public Integer convertWithValueOf(String str){\r\n    try {\r\n        Integer num = Integer.valueOf(str);\r\n        return num;\r\n    }\r\n    catch(NumberFormatException e){\r\n        return DEFAULT_PARSED_INT;\r\n    }\r\n}<\/pre>\n
Here is the JUnit test code.<\/p>\n
@Test\r\npublic void convertWithValueOf() {\r\n     int val= stringToIntConverter.convertWithValueOf(str);\r\n     System.out.println(val);\r\n     assertEquals(val, 369);\r\n }\r\n<\/pre>\n
The test output is this.<\/p>\n
\"Java<\/a><\/p>\n
Note<\/strong>: Similar to parseInt(), the valueOf() method also have an overloaded version that accepts an additional radix value.<\/p>\n
Conclusion<\/h1>\n
Considering Java is a strongly typed language and often interfaces with systems that do not have the type system of Java, converting from a string value to an int value in Java is very common task.\u00a0As you can see Java provides a number of different ways to convert a string value to an integer value.<\/p>\n
 <\/p>\n","protected":false},"excerpt":{"rendered":"
A common requirement while programming in Java is to convert String to int. UI inputs in Web-based HTML, JSP, or Thymeleaf templates are transferred to backend Java applications as strings. It is the application developer\u2019s responsibility to perform any String to int conversions to fulfill business logic, such as calculating discounts, storing age, and so […]Continue reading<\/a><\/p>\n","protected":false},"author":1,"featured_media":4592,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_lmt_disableupdate":"","_lmt_disable":"","_monsterinsights_skip_tracking":false,"_monsterinsights_sitenote_active":false,"_monsterinsights_sitenote_note":"","_monsterinsights_sitenote_category":0,"_uf_show_specific_survey":0,"_uf_disable_surveys":false,"_jetpack_memberships_contains_paid_content":false,"footnotes":"","jetpack_publicize_message":"","jetpack_publicize_feature_enabled":true,"jetpack_social_post_already_shared":true,"jetpack_social_options":{"image_generator_settings":{"template":"highway","enabled":false},"version":2}},"categories":[20],"tags":[27,198],"class_list":["post-4077","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-java","tag-java","tag-string-to-int"],"jetpack_publicize_connections":[],"aioseo_notices":[],"modified_by":"Simanta","jetpack_sharing_enabled":true,"jetpack_featured_media_url":"https:\/\/springframework.guru\/wp-content\/uploads\/2015\/03\/Banner560x292_07web.jpg","jetpack_shortlink":"https:\/\/wp.me\/p5BZrZ-13L","_links":{"self":[{"href":"https:\/\/springframework.guru\/wp-json\/wp\/v2\/posts\/4077"}],"collection":[{"href":"https:\/\/springframework.guru\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/springframework.guru\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/springframework.guru\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/springframework.guru\/wp-json\/wp\/v2\/comments?post=4077"}],"version-history":[{"count":9,"href":"https:\/\/springframework.guru\/wp-json\/wp\/v2\/posts\/4077\/revisions"}],"predecessor-version":[{"id":5587,"href":"https:\/\/springframework.guru\/wp-json\/wp\/v2\/posts\/4077\/revisions\/5587"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/springframework.guru\/wp-json\/wp\/v2\/media\/4592"}],"wp:attachment":[{"href":"https:\/\/springframework.guru\/wp-json\/wp\/v2\/media?parent=4077"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/springframework.guru\/wp-json\/wp\/v2\/categories?post=4077"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/springframework.guru\/wp-json\/wp\/v2\/tags?post=4077"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}