首先來說一下InputStaram類是一個抽象類,不可以實例化(抽象類爲什麼不能實例化自行百度),java.io.InputStream類實現了Closeable接口 重寫了close()方法;但實際上close方法體是空的,具體的實現方法是有其子類實現的;
再說其read方法是一個抽象方法但其重載方法以及skip方法都是通過調用該抽象方法實現自己的的功能的,子類不再重寫;
java.io.InputStream類源碼
package java.io;
public abstract class InputStream implements Closeable {
private static final int MAX_SKIP_BUFFER_SIZE = 2048;
public abstract int read() throws IOException;
public int read(byte[] paramArrayOfByte) throws IOException {
return read(paramArrayOfByte, 0, paramArrayOfByte.length);
}
public int read(byte[] paramArrayOfByte, int paramInt1, int paramInt2) throws IOException {
if (paramArrayOfByte == null) {
throw new NullPointerException();
}
if ((paramInt1 < 0) || (paramInt2 < 0) || (paramInt2 > paramArrayOfByte.length - paramInt1)) {
throw new IndexOutOfBoundsException();
}
if (paramInt2 == 0) {
return 0;
}
int i = read();
if (i == -1) {
return -1;
}
paramArrayOfByte[paramInt1] = ((byte) i);
int j = 1;
try {
while (j < paramInt2) {
i = read();
if (i == -1) {
break;
}
paramArrayOfByte[(paramInt1 + j)] = ((byte) i);
j++;
}
} catch (IOException localIOException) {
}
return j;
}
public long skip(long paramLong) throws IOException {
long l = paramLong;
if (paramLong <= 0L) {
return 0L;
}
int j = (int) Math.min(2048L, l);
byte[] arrayOfByte = new byte[j];
while (l > 0L) {
int i = read(arrayOfByte, 0, (int) Math.min(j, l));
if (i < 0) {
break;
}
l -= i;
}
return paramLong - l;
}
public int available() throws IOException {
return 0;
}
public void close() throws IOException {
}
public synchronized void mark(int paramInt) {
}
public synchronized void reset() throws IOException {
throw new IOException("mark/reset not supported");
}
public boolean markSupported() {
return false;
}
}