Eclipse/Java code completion not working

Try restoring the default options in 'Windows > Preferences > Java > Editor > Content Assist > Advanced'

An example of the kind of data you see in this preference screen, however not necessarily what you currently have.

(From Vadim in this blog post " Content Assist Duplicates in Eclipse (Mylyn)":
if have duplicate Mylyn entries, uncheck the duplicate entries that do not contain "(Mylyn)" in their name)

The Eclipse help page defines the default list to restore:

Select the proposal kinds contained in the 'default' content assist list:

• Other Java Proposals,
• SWT Template Proposals,
• Template Proposals,
• Type Proposals

None of these worked for me.

I was experiencing this issue in only once particular class. What finally worked for me was to delete the offending class and recreate it. Problem solved... mystery not so much!

If you have installed Google Toolbar for IE, may be you can face the same problem. Because, the toolbar capture the shortcut ctrl+Space.

I faced this problem, and spent hours trying to figure out the issue. tried to follow the steps mentioned in the different answers above, the solution I found is on the same lines as Mona suggested, but slightly different. Tried to add as a comment to Mona's answer but no option was available. Issue with my eclipse was, classpath somehow got corrupted and all the jars and dependent projects were missing. after taking the latest .classpath from repository it worked fine.

Running STS on Java Spring Boot projects, here's what works for me :

Maybe this helps other people who come across the same issue.

My setup: old Gradle project (version Gradle 2.12) made by someone else, imported using the Gradle Import Wizard into STS (Eclipse Oxygen.2 (4.7.2)).

Code completion did not work either (and I still have hollow Js at the Java files), but at least I got the code completion to work by doing:

• right click on the project folder > Properties > Gradle > Configure Workspace Settings > Java > Editor > Content Assist > Advanced
• check "Java Proposals in upper window.
• 2x Apply & Close

I have run into this problem since upgrading to Eclipse 2019-09. Based on some of the suggestions above, this is what worked for me.

I had to go to Eclipse -> Preferences -> Java -> Editor -> Content Assist -> Advanced.

I found out that if I turn on any of the key binding proposals, Java Non-Type, Java, Java (Task-Focused) or Java Type proposal, then I was able to use auto complete. If I turned them all on, then not only did auto complete work, but I got duplicate methods listed. I am guessing, but I will probably used Java Type Proposals. Any clarification of what differs for these four types would be appreciated.

For those who use the latest 3-19 eclipse build:

It just happened to me when upgrading from Oxygen to 3-19 eclipse version, so I assume the auto-complete feature does not migrated correctly during the upgrade process.

The only solution that worked for me was to create a new eclipse workspace, and import the project/s to it. It might take a few minutes, but it worth it - comparing to the time spent on other solutions...

If you're experiencing this in an enum, or when initializing an array with anonymous classes, it's a known bug in Eclipse. See Eclipse content assist not working in enum constant parameter list.

We can change the settings as per our requirement.

Suppose we want to make java proposal as highest priority we need to do changes as shown below.

Windows > Preferences > Java > Editor > Content Assist > Advanced

Choose Java proposal and click on up button

For me in Sep 2021 it was an odd Eclipse bug. I had a multi-line string inside an annotation in my Class. This caused just that particular class to fail when trying to code complete (even though the class compiled just fine).