開始學習下java
主要是學習下java中的hashmap,順便溫習下構造函數
hashmap是java中用於存儲key-value鍵值對類型,而構造函數主要用於對class中的變量初始化,在new對象的時候,根據你傳入的參數的類型和長度來知道,你調用的是哪個構造函數。
package com.test;
import java.util.Collection;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import org.apache.commons.collections4.map.HashedMap;
public class TestArray {
public String name;
public String age;
public String sex;
double[] myList = new double[10];
public TestArray(String name, String age) {
this.name = name;
this.age = age;
}
public TestArray(String aa, String age, String name) {
this.name = name;
this.age = age;
this.sex = aa;
}
public String getAge() {
return age;
}
public static void main(String[] args) {
TestArray tArray = new TestArray("zhoux", "12");
System.out.println(tArray.getAge());
Map<String, String> infoMap = new HashMap<String, String>();
infoMap.put("1","1.1");
infoMap.put("2", "2.2");
Collection<String> cl = infoMap.values();
Collection<String> c2 = infoMap.keySet();
System.out.println(c2);
Iterator<String> iterator = c2.iterator();
while(iterator.hasNext()) {
System.out.println(iterator.next());
}
}
}
集合和數組
數組的長度在初始化的時候已經確定,集合是一個動態的數組,長度可變
package com.test;
import java.util.ArrayList;
public class TestList {
static ArrayList<String> listsArrayList = new ArrayList<String>();
public static void main(String[] args) {
//ArrayList 集合 是一個其容量能夠動態增長的動態數組
listsArrayList.add("par1");
listsArrayList.add("par2");
System.out.println(listsArrayList);
//循環讀取 集合用size() 數組用length
for (int i = 0; i < listsArrayList.size(); i++) {
System.out.println(listsArrayList.get(i));
}
/*
* 需要提前確定數組長度時
* */
double[] dlists = new double[2];
dlists[0]=1.1;
dlists[1]=1.2;
//循環讀取
for (int i = 0; i < dlists.length; i++) {
System.out.println(dlists[i]);
}
}
}