int   a   =   12345678901; 
char   str[4]; 
str[0]   =   (char)(a   &   0xff); 
str[1]   =   (char)((a   > >   8)   &   0xff); 
str[2]   =   (char)((a   > >   16)   &   0xff); 

str[3]   =   (char)((a   > >   24)   &   0xff);

将字符型转换字符串

通过String.valueOf(char)函数把字符转化成字符串

举例

char a='A';//定义一个字符a
String str = String.valueOf(a);//把字符a转换成字符串str

最简单的方法
char c = 'a';
String s = "" + c;

char[ ]转String

String str = String.valueOf(char[] data);

把字符串转化为输入流

public static InputStream getStringStream(String sInputString){
　　if (sInputString != null && !sInputString.trim().equals("")){
　　try{
　　ByteArrayInputStream tInputStringStream = new ByteArrayInputStream(sInputString.getBytes());
　　return tInputStringStream;
　　}catch (Exception ex){
　　ex.printStackTrace();
　　}
　　}
　　return null;
}

//

//txt为TextArea内的字符串

try{
InputStream myIn=new ByteArrayInputStream(txt.getBytes("UTF-8"));
//将System.in转化为面向字符的流
InputStreamReader ir = new InputStreamReader(myIn);

in = new BufferedReader(ir);//为输入流提供缓冲区

while ((s = in.readLine()) != "bye") 
System.out.println("Read: " + s);

}
catch(IOException e)
{System.out.println("Error! ");}
}

//

import java.io.BufferedReader;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;

class ReadByte {
public static void main(String[] args) {
try {
BufferedReader br = new BufferedReader(new FileReader(
"c:/bsmain_runtime.log"));
String s;
while (br.ready() && (s = br.readLine()) != "bye") {
System.out.println("Read: " + s);
}
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}
} 

以上是直接从文件
===================
一下是从String

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.PipedReader;
import java.io.PipedWriter;
import java.io.PrintWriter;

class ReadByte {
public static void main(String[] args) {
try {
String test = "1234\r\nsdfs";
PipedWriter pw = new PipedWriter();
PipedReader pr = new PipedReader(pw);
PrintWriter pw2 = new PrintWriter(new BufferedWriter(pw), true);
BufferedReader br = new BufferedReader(pr);
pw2.println(test);

String s;
while (br.ready() && (s = br.readLine()) != "bye") {
System.out.println("Read: " + s);
}
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}

}