str.split("[^\\w\\s]+")[0]
Это будет соответствовать всем последовательным символам [a-zA-Z_0-9] и пробелам в начале строки
List<String> str = new ArrayList<String>();
str.add("TEXT1.more text ");
str.add("TEXT1)more text ");
str.add("TEXT1}more text ");
str.add("Beginning text Text I want . Text I don't want");
str.add("Beginning text with numbers Text I want ( Text I don't want )");
str.add("Beginning text with numbers Text I want { Text I don't want }");
for(String s : str)
System.out.println("input: [" + s + "], first word: " + s.split("[^\\w\\s]+")[0]);
производит:
input: [TEXT1.more text ], first word: TEXT1
input: [TEXT1)more text ], first word: TEXT1
input: [TEXT1}more text ], first word: TEXT1
input: [Beginning text Text I want . Text I don't want], first word: Beginning text Text I want
input: [Beginning text with numbers Text I want ( Text I don't want )], first word: Beginning text with numbers Text I want
input: [Beginning text with numbers Text I want { Text I don't want }], first word: Beginning text with numbers Text I want