Bug 16858 Preceding space in package compression pattern sometimes ignored
(In the following discussion, all patterns were entered without the enclosing quote marks.) The pattern "1 " causes one character of each package name to be displayed with a single space separator between them. The pattern " 1 " causes one space to precede the first single-character package name and two spaces to appear between each one. Both of the above cases were expected. However, if you set the patttern to " 1" (i.e. space before, but no space after), no spaces are displayed in the result.
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/viewsupport/JavaElementLabels.java
public static void getTypeLabel(IType type, int flags, StringBuffer buf) {
		if (getFlag(flags, T_FULLY_QUALIFIED)) {
			buf.append(JavaModelUtil.getFullyQualifiedName(type));
		} else if (getFlag(flags, T_CONTAINER_QUALIFIED)) {
			buf.append(JavaModelUtil.getTypeQualifiedName(type));
		} else {
			buf.append(type.getElementName());
		}
		
		if (getFlag(flags, T_POST_QUALIFIED)) {
			buf.append(CONCAT_STRING);
			IType declaringType= type.getDeclaringType();
			if (declaringType != null) {
				buf.append(JavaModelUtil.getFullyQualifiedName(declaringType));
			} else {
				getPackageFragmentLabel(type.getPackageFragment(), 0, buf);
			}
		}
	}
	/**
	 * Appends the label for a declaration to a StringBuffer. Considers the D_* flags.
	 */	
	public static void getDeclararionLabel(IJavaElement declaration, int flags, StringBuffer buf) {
		if (getFlag(flags, D_QUALIFIED)) {
			IJavaElement openable= (IJavaElement) declaration.getOpenable();
			if (openable != null) {
				buf.append(getElementLabel(openable, CF_QUALIFIED | CU_QUALIFIED));
				buf.append('/');
			}	
		}