链表、装箱与拆箱

链表

基本形式（依赖于引用传递和this调用当前对象）

class Node{
    private String data;   //要保存的数据
    private Node next;  //要保存的下一节点
    public Node(String data){    //保存相对应的数据
        this.data = data;
    }
    public void setNext(Node next){
        this.next = next;
    }
    public Node getNext(){
        return this.next;
    }
    public String getData(){
        return this.data;
    }
}
public class ListNode{
    public static void main(String []args){
        Node root = new Node("火车头");
        Node n1 = new Node("车厢A");
        Node n2 = new Node("车厢B");
        root.setNext(n1);
        n1.setNext(n2);
        Node current = root;
        while(current != null){
            System.out.println(current.getData());
            current = current.getNext();
        }
    }
}

装箱与拆箱

int与Integer

public class ListNode{
    public static void main(String []args){
        Integer obj = new Integer(10);
        int temp = obj.intValue();
        System.out.println(temp*2);
    }
}

double与Double

public class ListNode{
    public static void main(String []args){
        Double obj = new Double(10.2);
        Double temp = obj.doubleValue();
        System.out.println(temp*2);
    }
}

boolean与Boolean

public class ListNode{
    public static void main(String []args){
        Boolean obj = new Boolean(true);
        Boolean temp = obj.booleanValue();
        System.out.println(temp);
    }
}

自动拆箱与装箱

public class ListNode{
    public static void main(String []args){
        Integer obj = 10;  //自动装箱
        int temp = obj;    //自动拆箱
        obj++;
        System.out.println(temp*obj);
    }
}

与String对象一致

public class ListNode{
    public static void main(String []args){
        Integer obja = 10;  //自动装箱
        Integer objb = 10;
        Integer objc = new Integer(10);
        System.out.println(obja == objc);
        System.out.println(obja.equals(objc));
    }
}

Object可以接收一切的引用数据类型

public class ListNode{
    public static void main(String []args){
        Object obj = 10;
        int temp = (Integer)obj;
        System.out.println(temp*2);
    }
}

double必须给以指定的格式

public class ListNode{
    public static void main(String []args){
        Double obj = 10;
        System.out.println(obj);
    }
}
F:\prac>javac ListNode.java
ListNode.java:3: 错误: 不兼容的类型: int无法转换为Double
                Double obj = 10;
                             ^
1 个错误
---------------------------------------------------
public class ListNode{
    public static void main(String []args){
        Double obj = 10.2;
        System.out.println(obj);
    }
}

Boolean

public class ListNode{
    public static void main(String []args){
        Boolean flag = true;
        if(flag){
            System.out.println("Hello");
        }
    }
}

String与各个基本数据类型之间的转换操作
一、public static int parseInt(String s)

//被转换的数必须由数字组成
public class ListNode{
    public static void main(String []args){
        String str = "123";
        int temp = Integer.parseInt(str);
        System.out.println(temp*3);
    }
}

二、public static double parseDouble(String s)

public class ListNode{
    public static void main(String []args){
        String str = "1.3";
        double temp = Double.parseDouble(str);
        System.out.println(temp*3);
    }
}

三、public static boolean parseBoolean(String s)

//如果String的值不是true或false，则按false统一处理
public class ListNode{
    public static void main(String []args){
        String str = "true";
        boolean temp = Boolean.parseBoolean(str);
        if(temp){
            System.out.println("满足条件");
        }else{
            System.out.println("不满足条件");
        }
    }
}
F:\prac>java ListNode
满足条件
---------------------------------------------------------
public class ListNode{
    public static void main(String []args){
        String str = "xfxhfdnxde";
        boolean temp = Boolean.parseBoolean(str);
        if(temp){
            System.out.println("满足条件");
        }else{
            System.out.println("不满足条件");
        }
    }
}
F:\prac>java ListNode
不满足条件

String转基本数据类型
一、任何基本数据类型与String类型使用了“+”操作后均变为String类型

public class ListNode{
    public static void main(String []args){
        int num = 100;
        String str = num+"";
        System.out.println(str.replaceAll("0","9"));
    }
} 

二、public static String valueOf(数据类型 变量) public static String valueOf(int i)

public class ListNode{
    public static void main(String []args){
        int num = 100;
        String str = String.valueOf(num);
        System.out.println(str.replaceAll("0","9"));
    }
}