java核心技术 高级特性第八版 27页的有关问题

//这样有错class DataIO{    public static void writeFixedString(String name,int size,DataOutputStream out)             throws IOException{        int i=0;        char ch;        while(i<size){            ch=0;            if(i<name.length()){                ch=name.charAt(i);            }            out.writeChar(ch);            i++;        }    }    public static String readFixedString(int size,RandomAccessFile in)             throws IOException{        int i=0;        char ch;        StringBuilder str=new StringBuilder();        while(i<size){            ch=in.readChar();            if(ch==0)                break;            i++;            str.append(ch);        }        in.skipBytes(2*(size-i));        return str.toString();    }}/*改成这样问题是  if(ch=='0')      break;  从文本中读取'0'字符赋予ch，可ch不会等于'0'了，ch=='0'永远为假，这是为什么？*/class DataIO{    public static void writeFixedString(String name,int size,DataOutputStream out)             throws IOException{        int i=0;        char ch;        while(i<size){            ch=0;            if(i<name.length()){                ch=name.charAt(i);            }            out.writeChar(ch);            i++;        }    }    public static String readFixedString(int size,RandomAccessFile in)             throws IOException{        int i=0;        char ch;        StringBuilder str=new StringBuilder();        while(i<size){            ch=in.readChar();            if(ch=='0')                break;            i++;            str.append(ch);        }        in.skipBytes(2*(size-i));        return str.toString();    }}//换成这样也不对，到底是为什么，好纠结class DataIO{    public static void writeFixedString(String name,int size,DataOutputStream out)             throws IOException{        int i=0;        char ch;        while(i<size){            ch=' ';            if(i<name.length()){                ch=name.charAt(i);            }            out.writeChar(ch);            i++;        }    }    public static String readFixedString(int size,RandomAccessFile in)             throws IOException{        int i=0;        char ch;        StringBuilder str=new StringBuilder();        while(i<size){            ch=in.readChar();            if(ch==' ')                break;            i++;            str.append(ch);        }        in.skipBytes(2*(size-i));        return str.toString();    }}

class DataIO{    public static void writeFixedString(String name,int size,DataOutputStream out)             throws IOException{        int i=0;        char ch;        while(i<size){            ch=0;            if(i<name.length()){                ch=name.charAt(i);            }            out.writeChar(ch);            i++;        }    }    public static String readFixedString(int size,RandomAccessFile in)             throws IOException{        int i=0;        char ch;        StringBuilder str=new StringBuilder();        while(i<size){            ch=in.readChar();            if(ch==0)                break;            i++;            str.append(ch);        }        in.skipBytes(2*(size-i));        return str.toString();    }}
------解决方案--------------------
改成0的Assic 码，试试