Enable generate hashCode and equals source action

[testforstephen]

Signed-off-by: Jinbo Wang [email protected]

Feature #597.

Prompt to select fields to include:

[testforstephen]

Peer PR on eclipse.jdt.ls side eclipse-jdtls/eclipse.jdt.ls#940

[fbricon]

Couple of remarks so far (we can get rid of one prompt and improve the dialog - I like clear actionable choices ), but that's a promising start. I still need to get my head around the API though.

[fbricon]

I think we should expose at least one more option, to use instance of to perform comparisons.
So I'd change the preferences to have:

• "java.codeGeneration.hashcodeEquals.useJava7Objects".
• "java.codeGeneration.hashcodeEquals.compareInstanceOf"

Eventually, we might as well expose generateComments and useBrackets

[fbricon]

Here are the new preferences controlling the code generation:

• java.codeGeneration.hashCodeEquals.useJava7Objects: Use Objects.hash and Objects.equals when generating the hashCode and equals methods. This setting only applies to Java 7 and higher. Defaults to false.
• java.codeGeneration.hashCodeEquals.useInstanceof: Use 'instanceof' to compare types when generating the hashCode and equals methods. Defaults to false.
• java.codeGeneration.hashCodeEquals.useBlocks: Use blocks in 'if' statements when generating the hashCode and equals methods. Defaults to false.
• java.codeGeneration.hashCodeEquals.generateComments: Generate method comments when generating the hashCode and equals methods. Defaults to false.