贴一些演示简单API的代码
有部分使用不正确，不要模仿：/**
* enum
*/
package com;
/**
* @author Administrator
*
*/
public class EnumTest {
enum Week {
Mon, Tue, Wed, Thu, Fri, Sat, Sun
}
/**
* @param args
*/
public static void main(String[] args) {
System.out.println(Week.valueOf("Mon"));
//
System.out.println(Week.Mon);
System.out.println(Week.Sun);
Week[] w = Week.values();
for (Week we : w) {
System.out.println(we);
}
switch (Week.Sun) {
case Mon:
System.out.println("1");
break;
default:
System.out.println("default");
}
System.out.println(Week.Mon.compareTo(Week.Fri));
System.out.println(Coffee.small);
System.out.println(Coffee.small.getSize());
Coffee[] coffee = Coffee.values();
for(Coffee c: coffee) {
System.out.println(c);
System.out.println(c.getSize());
}
System.out.println(Week.valueOf("Mon1"));
}
}
enum Coffee {
small(8), middle(10), large(12);
private int size;
Coffee(int size) {
this.size = size;
}
public int getSize() {
return size;
}
}
Exception in thread "main" java.lang.IllegalArgumentException: No enum const class com.EnumTest$Week.Mon1
at java.lang.Enum.valueOf(Enum.java:196)
at com.EnumTest$Week.valueOf(EnumTest.java:1)
at com.EnumTest.main(EnumTest.java:48)
Mon
Mon
Sun
Mon
Tue
Wed
Thu
Fri
Sat
Sun
default
-4
small
8
small
8
middle
10
large
12
/**
*
*/
package com;
/**
* @author Administrator
*
*/
public class ForTest {
public static void main(String[] args) {
for (int i = 0, j = 10; i < 10;) {
System.out.println(i + j);
i++;
}
}
}
10
11
12
/**
*
*/
package com;
import java.util.ArrayList;
import java.util.List;
/**
* @author Administrator
*
*/
public class TestWildcards {
public static void main(String[] args) {
List<Integer> myList = new ArrayList<Integer>();
Bar bar = new Bar();
bar.doInsert(myList);
}
}
class Bar {
void doInsert(List<? extends Object> list) {
list.contains(new Dog());
// 说不清楚具体是什么 可添加多种对象而造成危险 比如 Cat Dog等。
list.add(new Object); // compile error
}
}
class Bar2 {
void doInsert(List<? super String> list) {
list.contains(new Dog());
// string is a ? 合理
list.add("test");
}
}
import java.util.Comparator;
import java.util.PriorityQueue;
/**
*
*/
/**
* @author Administrator
*
*/
public class PriorityQueueTest {
static class PQsort implements Comparator<Integer> { // inverse sort
public int compare(Integer one, Integer two) {
return two - one; // unboxing
}
}
public static void main(String[] args) {
int[] ia = { 1, 5, 3, 7, 6, 9, 8 }; // unordered data
PriorityQueue<Integer> pq1 = new PriorityQueue<Integer>(); // use
// natural
// order
for (int x : ia)
// load queue
pq1.offer(x);
for (int x : ia)
// review queue
System.out.print(pq1.poll() + " ");
System.out.println("");
PQsort pqs = new PQsort(); // get a Comparator
PriorityQueue<Integer> pq2 = new PriorityQueue<Integer>(10, pqs); // use
// Comparator
for (int x : ia)
// load queue
pq2.offer(x);
System.out.println("size " + pq2.size());
System.out.println("peek " + pq2.peek());
System.out.println("size " + pq2.size());
System.out.println("poll " + pq2.poll());
System.out.println("size " + pq2.size());
for (int x : ia)
// review queue
System.out.print(pq2.poll() + " ");
}
}
1 3 5 6 7 8 9
size 7
peek 9
size 7
poll 9
size 6
8 7 6 5 3 1 null
/**
*
*/
package com;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.List;
/**
* @author Administrator
*
*/
public class CollectionsTest {
/**
* @param args
*/
public static void main(String[] args) {
List list = new ArrayList();
list.add("a");
list.add("b");
list.add("c");
list.add("a23");
Collections.sort(list);
int i = Collections.binarySearch(list, "a23");
System.out.println(list);
PQsort pq = new PQsort();
Collections.sort(list,pq);
int j = Collections.binarySearch(list, "a23");
System.out.println(i);
System.out.println(j);
int m = Collections.binarySearch(list, "a23", pq);
System.out.println(m);
System.out.println(list);
}
}
class PQsort implements Comparator<String> { // inverse sort
public int compare(String one, String two) {
return two.compareTo(one); // unboxing
//return one.compareTo(two); // unboxing
}
}
1
-1
2
/**
*
*/
package file;
import java.io.BufferedReader;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.io.Serializable;
/**
* @author Administrator
*
*/
public class FileTest implements Serializable {
public static void main(String[] args) {
String filePath = "d://test";
File file = new File(filePath);
file.mkdir();
File fileName = new File("d://test//t.dat");
try {
fileName.createNewFile();
<span style="font-size: small;"><span style="font-family: Times New Roman;"> } catch (IOException e)
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