java类contains问题

public class ArrayListtest {
public static void main(String[] args) {

String test = "TEST lesson nine";

boolean result1 = test.contains("TEST");
boolean result2 = test.contains("lesson");
boolean result3 = test.contains("NINE");
boolean result4 = test.contains("oas lesson nine");//不包含则为FALSE

System.out.println("result1:"+result1+"\t"+"result2:"+result2+"\t"+"result3:"+result3+"\t"+"result4:"+result4);

}
}

================result============================

result1:true result2:true result3:false result4:false

=====================why=================================

含有完全的字符串时才返回true。
当且仅当此字符串包含指定的 char 值序列时，返回 true即对于指定的字符串要完全匹配.