Here you can find the source of contains(final CharSequence seq, final CharSequence searchSeq)
public static boolean contains(final CharSequence seq, final CharSequence searchSeq)
//package com.java2s; public class Main { public static boolean contains(final CharSequence seq, final CharSequence searchSeq) { if (seq == null || searchSeq == null) { return false; }/* ww w.j a v a 2 s .com*/ return seq.toString().indexOf(searchSeq.toString()) >= 0; } }