base64标准编码的解码的java实现 已经给出了Ddelphi的实现

[tangxin123]

function Base64Decode(const s: string): string;
var
  i,m,n: Integer;
  c1,c2,c3,c4: Integer;
const
  Base64: string = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/';
begin
  Result := '';
  n:=1;
  m:=Length(s);
  if s[m]='='then m:=m-1;
  if s[m]='='then m:=m-1;
  for i:=1 to m div 4 do
  begin
    c1:=Pos(s[n],Base64)-1;
    c2:=Pos(s[n+1],Base64)-1;
    c3:=Pos(s[n+2],Base64)-1;
    c4:=Pos(s[n+3],Base64)-1;
    n:=n+4;
    Result:=Result+Chr(((c1 shl 2)and $FC)or((c2 shr 4)and $3));
    Result:=Result+Chr(((c2 shl 4)and $F0)or((c3 shr 2)and $0F));
    Result:=Result+Chr(((c3 shl 6)and $C0)or c4);
  end;
  if m mod 4=2 then
  begin
    c1:=Pos(s[n],Base64)-1;
    c2:=Pos(s[n+1],Base64)-1;
    Result:=Result+Chr(((c1 shl 2)and $FC)or((c2 shr 4)and $3));
  end;
  if m mod 4=3 then
  begin
    c1:=Pos(s[n],Base64)-1;
    c2:=Pos(s[n+1],Base64)-1;
    c3:=Pos(s[n+2],Base64)-1;
    Result:=Result+Chr(((c1 shl 2)and $FC)or((c2 shr 4)and $3));
    Result:=Result+Chr(((c2 shl 4)and $F0)or((c3 shr 2)and $0F));
  end;
end;

求java代码 只需要解码

[bianhei000]

不是有API么 直接调之

[lyhmy]

不懂，友情帮顶

[williamxiao]

下个工具包commons-codec,在org.apache.commons.codec.binary包中有Base64类,
使用其中的public static byte[] decodeBase64(String base64String)函数.

[tangxin123]

楼上的 那些貌似都不是标准编码的

[tangxiao890923]

public class Base64 {
	private static final String base64 = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";

	public static final String decode(final String s){
		int i,m,n,c1,c2,c3,c4;
		n = 0;
		m = s.length();
		ByteBuffer bu = ByteBuffer.allocate(m-(m/4));
		if(s.charAt(m-1)=='='){
			m--;
		}
		if(s.charAt(m-1)=='='){
			m--;
		}
		for(i=1;i<=m/4;i++){
			c1 = base64.indexOf(s.charAt(n));
			c2 = base64.indexOf(s.charAt(n+1));
			c3 = base64.indexOf(s.charAt(n+2));
			c4 = base64.indexOf(s.charAt(n+3));
			n+=4;
			bu.put((byte)(((c1<<2)&0xFC)|((c2>>4)&0x3)));
			bu.put((byte)(((c2<<4)&0xF0)|((c3>>2)&0x0F)));
			bu.put((byte)(((c3<<6)&0xC0)|c4));
		}
		
		if(m%4==2){
			c1 = base64.indexOf(s.charAt(n));
			c2 = base64.indexOf(s.charAt(n+1));
			bu.put((byte)(((c1<<2)&0xFC)|((c2>>4)&0x3)));
		}
		if(m%4==3){
			c1 = base64.indexOf(s.charAt(n));
			c2 = base64.indexOf(s.charAt(n+1));
			c3 = base64.indexOf(s.charAt(n+2));
			bu.put((byte)(((c1<<2)&0xFC)|((c2>>4)&0x3)));
			bu.put(((byte)(((c2<<4)&0xF0)|((c3>>2)&0x0F))));
		}
		return EncodingUtil.bytes2HexString(bu.array());
	}
}

[tangxin123]

[Quote=引用 5 楼 tangxiao890923 的回复:]
Java code


public class Base64 {
private static final String base64 = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";

public static final String decode(final String……
[/Quote]
嗯 验证了 是对的 谢谢