Bug 115711 [content assist] Parameter hints disappear immediately
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/text/java/ExperimentalProposal.java
char[][] parameterNames= fProposal.findParameterNames(null);
		int count= parameterNames.length;
		fArgumentOffsets= new int[count];
		fArgumentLengths= new int[count];
		StringBuffer buffer= new StringBuffer(String.valueOf(fProposal.getName()));
		
		FormatterPrefs prefs= getFormatterPrefs();
		if (prefs.beforeOpeningParen)
			buffer.append(SPACE);
		buffer.append(LPAREN);
		
		if (prefs.afterOpeningParen)
			buffer.append(SPACE);
		
		for (int i= 0; i != count; i++) {
			if (i != 0) {
				if (prefs.beforeComma)
					buffer.append(SPACE);
				buffer.append(COMMA);
				if (prefs.afterComma)
					buffer.append(SPACE);
			}
			
			fArgumentOffsets[i]= buffer.length();
			buffer.append(parameterNames[i]);
			fArgumentLengths[i]= parameterNames[i].length;
		}
		
		if (prefs.beforeClosingParen)
			buffer.append(SPACE);