[英]Interface implementation in static class
我正在嘗試理解一個Java代碼,這是代碼
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);
}
}
}
疑問:
1)InputReader是Test類的內部類,其中SpaceCharFilter接口是使用聲明的一個方法創建的。 我只看到可以通過在類上使用實現來使用接口的地方,例如,類實現接口{實現方法},但是在這種情況下,它是使用類的變量過濾器設置的。 我可以知道該功能在Java中如何工作嗎?
2)在isSpaceChar(int c)方法中,過濾器變量的意義是什么? 過濾器變量中可以包含哪些類型的值?
3)我正在使用此輸入“ 10 2”運行代碼,然后輸入。 理想情況下,它應該從is的輸入字符“ 10 2”中讀取輸入的“ 0”中的第二個字符時,在isSpaceChar方法中使用filter!= null條件,但它沒有進行,請問為什么?
誰能幫助我消除這些疑問?
這就是多態性的含義 :我們定義一個接口並調用其中定義的方法,而不關心實際的實現是什么(但希望實現與接口協定相匹配,后者由接口名稱,名稱來定義)其中定義的方法及其可能包含的任何注釋)。
它可以保存一個實現SpaceCharFilter
的對象。
這是因為變量filter
從不分配對象。 因此,接口和變量在此代碼中均無用 。
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