Uploaded image for project: 'JDK'
  1. JDK
  2. JDK-8330252

TreeMap<Object,Object> with different types of keys

    XMLWordPrintable

Details

    Description

      ADDITIONAL SYSTEM INFORMATION :
      $ uname -a
      Linux name 6.5.0-27-generic #28~22.04.1-Ubuntu SMP PREEMPT_DYNAMIC Fri Mar 15 10:51:06 UTC 2 x86_64 x86_64 x86_64 GNU/Linux

      $ java -version
      openjdk version "22" 2024-03-19
      OpenJDK Runtime Environment (build 22+36-2370)
      OpenJDK 64-Bit Server VM (build 22+36-2370, mixed mode, sharing)


      A DESCRIPTION OF THE PROBLEM :
      public class BugTreeMap {

          public static void main(String[] args) {
              java.util.Map<Object,Object> map = new java.util.TreeMap<>();
              map.put("a", "b");
      System.err.println("map.get(\"a\")="+map.get("a"));
              map.put(1, "a");
      System.err.println("map.get(1)="+map.get(1));
          }

      }

      /*
      When using a TreeMap with different types of keys, the code compiles but fails to run. The first error is gotten by running the program above. The second error is gotten by switching the map.put order. Expectation is to allow different types of keys and be able to get their respective values since the Map key and value types are both Object.

      $ java BugTreeMap
      map.get("a")=b
      Exception in thread "main" java.lang.ClassCastException: class java.lang.String cannot be cast to class java.lang.Integer (java.lang.String and java.lang.Integer are in module java.base of loader 'bootstrap')
              at java.base/java.lang.Integer.compareTo(Integer.java:74)
              at java.base/java.util.TreeMap.put(TreeMap.java:849)
              at java.base/java.util.TreeMap.put(TreeMap.java:569)
              at BugTreeMap.main(BugTreeMap.java:8)

      $ java BugTreeMap
      map.get(1)=a
      Exception in thread "main" java.lang.ClassCastException: class java.lang.Integer cannot be cast to class java.lang.String (java.lang.Integer and java.lang.String are in module java.base of loader 'bootstrap')
              at java.base/java.lang.String.compareTo(String.java:144)
              at java.base/java.util.TreeMap.put(TreeMap.java:849)
              at java.base/java.util.TreeMap.put(TreeMap.java:569)
              at BugTreeMap.main(BugTreeMap.java:8)

      */


      STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
      In a shell terminal:
      Save code as BugTreeMap.java
      Compile: javac BugTreeMap.java
      Run: java BugTreeMap

      EXPECTED VERSUS ACTUAL BEHAVIOR :
      EXPECTED -
      Expected result should be the output of the println statements.
      ACTUAL -
      Actual result is the errors shown in the description.

      ---------- BEGIN SOURCE ----------
      See the description.
      ---------- END SOURCE ----------

      CUSTOMER SUBMITTED WORKAROUND :
      Workaround is using a HashMap instead.

      FREQUENCY : always


      Attachments

        Activity

          People

            asajeev Anjana Sajeev
            webbuggrp Webbug Group
            Votes:
            0 Vote for this issue
            Watchers:
            3 Start watching this issue

            Dates

              Created:
              Updated:
              Resolved: