Databases
StackOverflow2013
Postsdbo
PO
 

Note that there are some explanatory texts on larger screens.

plurals
  1. PO
    primarykey
    data
    text
    <p><code>==</code> tests for reference equality (whether they are the same object).</p> <p><code>.equals()</code> tests for value equality (whether they are logically "equal"). </p> <p><a href="http://docs.oracle.com/javase/7/docs/api/java/util/Objects.html#equals(java.lang.Object,%20java.lang.Object)" rel="noreferrer">Objects.equals()</a> checks for <code>null</code> before calling <code>.equals()</code> so you don't have to (available as of JDK7, also available in <a href="https://github.com/google/guava/wiki/CommonObjectUtilitiesExplained#equals" rel="noreferrer">Guava</a>).</p> <p><a href="https://docs.oracle.com/javase/8/docs/api/java/lang/String.html#contentEquals-java.lang.CharSequence-" rel="noreferrer">String.contentEquals()</a> compares the content of the <code>String</code> with the content of any <code>CharSequence</code> (available since Java 1.5).</p> <p>Consequently, if you want to test whether two strings have the same value you will probably want to use <code>Objects.equals()</code>.</p> <pre><code>// These two have the same value new String("test").equals("test") // --&gt; true // ... but they are not the same object new String("test") == "test" // --&gt; false // ... neither are these new String("test") == new String("test") // --&gt; false // ... but these are because literals are interned by // the compiler and thus refer to the same object "test" == "test" // --&gt; true // ... string literals are concatenated by the compiler // and the results are interned. "test" == "te" + "st" // --&gt; true // ... but you should really just call Objects.equals() Objects.equals("test", new String("test")) // --&gt; true Objects.equals(null, "test") // --&gt; false Objects.equals(null, null) // --&gt; true </code></pre> <p>You almost <strong>always</strong> want to use<code>Objects.equals()</code>. In the <strong>rare</strong> situation where you <strong>know</strong> you're dealing with <a href="https://docs.oracle.com/javase/8/docs/api/java/lang/String.html#intern--" rel="noreferrer">interned</a> strings, you <em>can</em> use <code>==</code>.</p> <p>From <a href="https://docs.oracle.com/javase/specs/jls/se8/html/jls-3.html#jls-3.10.5" rel="noreferrer">JLS 3.10.5. <em>String Literals</em></a>:</p> <blockquote> <p>Moreover, a string literal always refers to the <em>same</em> instance of class <code>String</code>. This is because string literals - or, more generally, strings that are the values of constant expressions (<a href="https://docs.oracle.com/javase/specs/jls/se8/html/jls-15.html#jls-15.28" rel="noreferrer">§15.28</a>) - are "interned" so as to share unique instances, using the method <code>String.intern</code>.</p> </blockquote> <p>Similar examples can also be found in <a href="https://docs.oracle.com/javase/specs/jls/se8/html/jls-3.html#d5e1634" rel="noreferrer">JLS 3.10.5-1</a>.</p>
    singulars
    1. This table or related slice is empty.
    1. POHow do I compare strings in Java?
      singulars
      1. PTQuestion
    1. PTAnswer
    1. USCarlos Heuberger
    1. USAaron Maenpaa
    plurals
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. POHow do I compare strings in Java?
      singulars
      1. PTQuestion
    1. This table or related slice is empty.
    1. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTUpMod
    2. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTUpMod
    3. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTUpMod
    1. COI guess in Java you should say "references" instead of "pointers".
      singulars
      1. PO
      1. USHenrik Paul
    2. COIf you can do things this way, what is the method compareTo useful for?
      singulars
      1. PO
      1. USxocasdashdash
    3. CO@Xokas11: compareTo is generally used for sorting.
      singulars
      1. PO
      1. USMichael Myers
 

Querying!

 
Guidance
A row detail

Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

Related data can be related in a to-one or a to-many fashion. Captions of data related in a to-many fashion link to a list view showing a filtered view of the table.

Try moving around until you find a non-empty to-many entry and click on the label to get to one. You can move back to the root by clicking on the database name in the header.

SQuiL has stopped working due to an internal error.

If you are curious you may find further information in the browser console, which is accessible through the devtools (F12).

Reload