Bug 49182 What should canceling setRawClasspath do ?
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/preferences/OptionsConfigurationBlock.java
int nTokens= tok.countTokens();
		String[] res= new String[nTokens];
		for (int i= 0; i < res.length; i++) {
			res[i]= tok.nextToken().trim();
		}
		return res;
	}	
	
	public boolean performOk(boolean enabled) {
		String[] allKeys= getAllKeys();
		Map actualOptions= getOptions(false);
		
		
		boolean hasChanges= false;
		for (int i= 0; i < allKeys.length; i++) {
			String key= allKeys[i];
			String oldVal= (String) actualOptions.get(key);
			String val= null;
			if (enabled) {
				val= (String) fWorkingValues.get(key);
				if (!val.equals(oldVal)) {
					hasChanges= true;
					actualOptions.put(key, val);
				}
			} else {
				if (oldVal != null) {
					actualOptions.remove(key);
					hasChanges= true;
				}
			}