How do i check if something is an instance of String

Question

What is the syntax to use instance of without an array

com/example/BlogPost.java

package com.example;

import java.util.Date;

public class BlogPost {
    private String mAuthor;
    private String mTitle;
    private String mBody;
    private String mCategory;
    private Date mCreationDate;

    public BlogPost(String author, String title, String body, String category, Date creationDate) {
      mAuthor = author;
      mTitle = title;
      mBody = body;
      mCategory = category;
      mCreationDate = creationDate;
    }

    public String getAuthor() {
      return mAuthor;
    }

    public String getTitle() {
      return mTitle;
    }

    public String getBody() {
      return mBody;
    }

    public String getCategory() {
      return mCategory;
    }

    public Date getCreationDate() {
      return mCreationDate;
    }
}

TypeCastChecker.java

import com.example.BlogPost;

public class TypeCastChecker {
  /***************
  I have provided 2 hints for this challenge.
  Change `false` to `true` in one line below, then click the "Check work" button to see the hint.
  NOTE: You must set all the hints to false to complete the exercise.
  ****************/
  public static boolean HINT_1_ENABLED = false;
  public static boolean HINT_2_ENABLED = false;

  public static String getTitleFromObject(Object obj) {
    // Fix this result variable to be the correct string.
    String result = (String) obj;
    return result;
  }getTitleFromObject instanceof String

}

Answer 1 · 2017-03-02T20:50:59Z

March 2, 2017 8:50pm

Hi Robin,

You want to test if obj is a String object. You know you need to use instanceof for this. If obj is a String cast it and return it. You need an if statement to do the test first, then do the return statement if the test is true. Try something like:

  public static String getTitleFromObject(Object obj) {
    // Fix this result variable to be the correct string.
    if(obj instanceof String){
      return (String) obj;
    }
// next part here
    return ""; 
  }

Make sense? Shout if not and I'll explain further.

Steve.

Answer 2 · 2017-07-28T00:42:02Z

July 28, 2017 12:42am

The easiest solution is:

OBJECT_VARIABLE instanceof String

Answer 3 · 2017-03-02T20:54:25Z

March 2, 2017 8:54pm

The syntax (regadless of wheter the value is an array or not) is:

VALUE/VARIABLE_NAME instanceof TYPE

So if you had a variable called test and wanted to figure out if it was a string then the code would look something like this:

if (test instanceof String) {
    // inctanceof returns either true or false, so if this runs then it is a string.
}

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Robin Tadimeti

Robin Tadimeti

How do i check if something is an instance of String

3 Answers

Steve Hunter

Steve Hunter

Chris Adamson

Chris Adamson

andren

andren