我试图理解一个java代码，这里是代码
package RestClient;
import java.io.OutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.PrintWriter;
import java.io.PrintStream;
import java.io.BufferedWriter;
import java.io.Writer;
import java.io.OutputStreamWriter;
import java.util.InputMismatchException;
import java.io.IOException;
import java.io.InputStream;
public class Test {
public static void main(String[] args) {
InputStream inputStream = System.in;
System.out.println("Its done");
OutputStream outputStream = System.out;
InputReader in = new InputReader(inputStream);
OutputWriter out = new OutputWriter(outputStream);
TaskE solver = new TaskE();
solver.solve(1, in, out);
out.close();
}
static class TaskE {
static long[] dp;
static long[] sum;
static int n;
static SegmentTreeRMQ tree;
public void solve(int testNumber, InputReader in, OutputWriter out) {
System.out.println("2");
n = in.nextInt();
System.out.println("It always come Here");
int c = in.nextInt();
if (c == 1) {
out.println(0);
return;
}
int[] a = in.nextIntArray(n);
dp = new long[n];
sum = new long[n + 1];
for (int i = 1; i <= n; i++) {
sum[i] = sum[i - 1] + a[i - 1];
}
tree = new SegmentTreeRMQ();
tree.constructST(a, n);
out.println(comp(a, 0, n - 1, c));
}
private long comp(int[] a, int l, int r, int c) {
//System.out.println(l+" "+r);
if (r < l) return 0;
if (r == l && c == 1) return 0;
else if (r == l) return a[l];
if (dp[l] != 0) return dp[l];
int min = a[l];
long val = sum[r + 1] - sum[l];
val = Math.min(val, (a[l] + comp(a, l + 1, r, c)));
if (l + c <= n)
val = Math.min(val, sum[l + c] - sum[l] - tree.RMQ(n, l, l + c - 1) + comp(a, l + c, r, c));
//System.out.println("val:"+l+" "+val);
dp[l] = val;
return val;
}
}
static class InputReader {
private InputStream stream;
private byte[] buf = new byte[1024];
private int curChar;
private int numChars;
private InputReader.SpaceCharFilter filter;
public InputReader(InputStream stream) {
System.out.println("1");
this.stream = stream;
}
public int read() {
System.out.println("Its4");
System.out.println("numChars Near 4: " +numChars);
System.out.println("curChar Near 4: " +curChar);
if (numChars == -1) {
throw new InputMismatchException();
}
if (curChar >= numChars) {
curChar = 0;
try {
System.out.println("5");
numChars = stream.read(buf);
System.out.println("numChars: "+numChars);
System.out.println("Print: "+new String(new byte[]{ (buf[curChar]) }, "US-ASCII"));
} catch (IOException e) {
throw new InputMismatchException();
}
if (numChars <= 0) {
return -1;
}
}
System.out.println("curChar++: "+curChar);
return buf[curChar++];
}
public int nextInt() {
System.out.println("3");
int c = read();
System.out.println("c: "+c);
while (isSpaceChar(c)) {
System.out.println("6");
c = read();
}
int sgn = 1;
System.out.println("7");
if (c == '-') {
System.out.println("8");
sgn = -1;
c = read();
}
int res = 0;
do {
if (c < '0' || c > '9') {
throw new InputMismatchException();
}
System.out.println("9");
res = res*10;
res = res+c - '0';
c = read();
} while (!isSpaceChar(c));
return res * sgn;
}
public boolean isSpaceChar(int c) {
if (filter != null) {
System.out.println("here");
return filter.isSpaceChar(c);
}
return isWhitespace(c);
}
public static boolean isWhitespace(int c) {
return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
}
public int[] nextIntArray(int n) {
int[] array = new int[n];
for (int i = 0; i < n; ++i) array[i] = nextInt();
return array;
}
public interface SpaceCharFilter {
public boolean isSpaceChar(int ch);
}
}
static class SegmentTreeRMQ {
int[] st;
int minVal(int x, int y) {
return (x < y) ? x : y;
}
int getMid(int s, int e) {
return s + (e - s) / 2;
}
int RMQUtil(int ss, int se, int qs, int qe, int index) {
// If segment of this node is a part of given range, then
// return the min of the segment
if (qs <= ss && qe >= se)
return st[index];
// If segment of this node is outside the given range
if (se < qs || ss > qe)
return Integer.MAX_VALUE;
// If a part of this segment overlaps with the given range
int mid = getMid(ss, se);
return minVal(RMQUtil(ss, mid, qs, qe, 2 * index + 1),
RMQUtil(mid + 1, se, qs, qe, 2 * index + 2));
}
int RMQ(int n, int qs, int qe) {
// Check for erroneous input values
if (qs < 0 || qe > n - 1 || qs > qe) {
System.out.println("Invalid Input");
return -1;
}
return RMQUtil(0, n - 1, qs, qe, 0);
}
int constructSTUtil(int arr[], int ss, int se, int si) {
// If there is one element in array, store it in current
// node of segment tree and return
if (ss == se) {
st[si] = arr[ss];
return arr[ss];
}
// If there are more than one elements, then recur for left and
// right subtrees and store the minimum of two values in this node
int mid = getMid(ss, se);
st[si] = minVal(constructSTUtil(arr, ss, mid, si * 2 + 1),
constructSTUtil(arr, mid + 1, se, si * 2 + 2));
return st[si];
}
void constructST(int arr[], int n) {
// Allocate memory for segment tree
//Height of segment tree
int x = (int) (Math.ceil(Math.log(n) / Math.log(2)));
//Maximum size of segment tree
int max_size = 2 * (int) Math.pow(2, x) - 1;
st = new int[max_size]; // allocate memory
// Fill the allocated memory st
constructSTUtil(arr, 0, n - 1, 0);
}
}
static class OutputWriter {
private final PrintWriter writer;
public OutputWriter(OutputStream outputStream) {
writer = new PrintWriter(new BufferedWriter(new OutputStreamWriter(outputStream)));
}
public OutputWriter(Writer writer) {
this.writer = new PrintWriter(writer);
}
public void close() {
writer.close();
}
public void println(long i) {
writer.println(i);
}
public void println(int i) {
writer.println(i);
}
}
}
疑惑：
1）InputReader是Test类的内部类，其中SpaceCharFilter接口是使用声明的一个方法创建的。我已经看到只能通过在类上使用实现来使用接口，例如类实现接口{implements方法}，但在这种情况下，它是使用类的可变过滤器设置的。我可以知道这个功能在Java中是如何工作的吗？
2）在isSpaceChar（int c）方法中，filter变量的意义是什么？过滤器变量中可以包含哪些类型的值？
3）我使用此输入运行代码＆＃34; 10 2＆＃34;然后进入。理想情况下，它应该在isSpaceChar方法中过滤！= null条件，同时从输入读取第二个字符＆＃34; 0＆＃34;从＆＃34; 10 2＆＃34;，但它不会，我可以知道为什么？
有谁能帮我清除这些疑惑？
答案 0 :(得分：2)
这就是 polymorhism 的意义所在：我们定义一个接口并调用其中定义的方法而不关心实际的实现是什么（但期望实现与接口匹配） 合同，由接口名称，其中定义的方法名称及其可能的评论定义。
它可以容纳一个实现SpaceCharFilter的对象。
这是因为变量filter 从不获取分配的对象。
因此，此代码中的接口和变量都是无用的。