You can use following code segment:
String[] html = {"<H1>xxx</H2>","<font size=3>xxxx</font>"};
System.out.println(html[0].replaceAll("\\<.*?\\>",""));
System.out.println(html[1].replaceAll("\\<.*?\\>",""));
But if you need more advanced functionality, you can consider using a HTML parsing library instead:
HTML Parser - HTML Parser
Jericho HTML Parser