j2se/src/share/classes/java/awt/datatransfer/MimeTypeParameterList.java
j2se/src/share/classes/javax/activation/MimeTypeParameterList.java
j2se/src/share/classes/com/sun/activation/registries/MailcapTokenizer.java

all contain code that create default-sized StringBuffers and then immediately resize the buffer appropriately. It would be better if the StringBuffer were created with the appropriate size.

When someone is in fixing

    4945824: Should consider using StringBuilder instead of String/StringBuffer in AWT

they should look around for constructors that are followed by calls to ensureCapacity. Here are the calls that I found in the above files

    java/awt/datatransfer/MimeTypeParameterList.java:262: StringBuffer buffer = new StringBuffer();
    java/awt/datatransfer/MimeTypeParameterList.java:263: buffer.ensureCapacity(parameters.size() * 16);
    java/awt/datatransfer/MimeTypeParameterList.java:334: StringBuffer buffer = new StringBuffer();
    java/awt/datatransfer/MimeTypeParameterList.java:335: buffer.ensureCapacity((int)(length * 1.5));
    java/awt/datatransfer/MimeTypeParameterList.java:365: StringBuffer buffer = new StringBuffer();
    java/awt/datatransfer/MimeTypeParameterList.java:366: buffer.ensureCapacity(valueLength);
    javax/activation/MimeTypeParameterList.java:226: StringBuffer buffer = new StringBuffer();
    javax/activation/MimeTypeParameterList.java:227: buffer.ensureCapacity(parameters.size() * 16);
    javax/activation/MimeTypeParameterList.java:275: StringBuffer buffer = new StringBuffer();
    javax/activation/MimeTypeParameterList.java:276: buffer.ensureCapacity((int)(length * 1.5));
    javax/activation/MimeTypeParameterList.java:304: StringBuffer buffer = new StringBuffer();
    javax/activation/MimeTypeParameterList.java:305: buffer.ensureCapacity(valueLength);
    com/sun/activation/registries/MailcapTokenizer.java:256: StringBuffer buffer = new StringBuffer();
    com/sun/activation/registries/MailcapTokenizer.java:257: buffer.ensureCapacity(inputLength);

I'm filing this under classes_awt. If that's the wrong subcategory, feel free to recategorize this.