text: map store frequency of each character
code: HashMap < Character , Integer > m1 = new HashMap < > ( ) ; HashMap < Character , Integer > m2 = new HashMap < > ( ) ; for ( int i = 0 ; i < s1 . length ( ) ; i ++ ) { if ( m1 . containsKey ( s1 . charAt ( i ) ) ) { int x = m1 . get ( s1 . charAt ( i ) ) ; m1 . put ( s1 . charAt ( i ) , ++ x ) ; } else m1 . put ( s1 . charAt ( i ) , 1 ) ; } for ( int i = 0 ; i < s2 . length ( ) ; i ++ ) { if ( m2 . containsKey ( s2 . charAt ( i ) ) ) { int x = m2 . get ( s2 . charAt ( i ) ) ; m2 . put ( s2 . charAt ( i ) , ++ x ) ; } else m2 . put ( s2 . charAt ( i ) , 1 ) ; } for ( HashMap . Entry < Character , Integer > entry : m1 . entrySet ( ) ) {