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  • JAVA期末考试试题

    package z;
    
    import java.io.RandomAccessFile;
    
    public class J_Test1 {
    	public static void main(String[] args) throws Exception {
    		RandomAccessFile f = new RandomAccessFile("a.txt", "rw");
    		f.writeBoolean(true);
    		f.writeBoolean(false);
    		for (int i = 1; i < 10; ++i)
    			f.writeInt(i);
    		f.seek(1);
    		System.out.println(f.readInt());
    		f.close();
    	}
    }
    

    writeBoolean

    按单字节值将 boolean 写入该文件。值 true 写出为值 (byte)1;值false 写出为值(byte)0。写入从文件指针的当前位置开始。

    true false 1 2 3 4 5 6 7 8 9

    1 + 1 + 4

    所以输出为2


    package z;
    
    import java.io.RandomAccessFile;
    
    public class J_Test1 {
    	public static void main(String[] args) throws Exception {
    		RandomAccessFile f = new RandomAccessFile("a.txt", "rw");
    		f.writeBoolean(true);
    		f.writeBoolean(false);
    		for (int i = 1; i < 10; ++i)
    			f.writeInt(i);
    		f.seek(0);
    		System.out.println(f.readBoolean());
    		System.out.println(f.readBoolean());
    		for (int i = 1; i < 10; ++i){
    			System.out.print(f.readInt() + " ");
    		}
    		f.close();
    	}
    }
    


    package ss;
    
    class J_SuperClass {
    	int m_data = 0;
    
    	J_SuperClass() {
    		System.out.println("J_SuperClass::构造函数");
    		mb_add(1);
    	}
    
    	public void mb_add(int i) {
    		System.out.println("J_SuperClass::mb_add");
    		m_data += i;
    	}
    
    	public void mb_print() {
    		System.out.println(m_data);
    	}
    }
    
    class J_SubClass extends J_SuperClass {
    	J_SubClass() {
    		System.out.println("J_SubClass::构造函数");
    		mb_add(2);
    	}
    
    	public void mb_add(int i) {
    		System.out.println("J_SubClass::mb_add");
    		m_data += i * 2;
    	}
    }
    
    public class J_Test {
    	public static void main(String[] args) {
    		J_SuperClass a = new J_SubClass();
    		a.mb_print();
    		a.mb_add(6);
    		a.mb_print();
    	}
    }
    


    J_SuperClass::构造函数
    J_SubClass::mb_add
    J_SubClass::构造函数
    J_SubClass::mb_add
    6
    J_SubClass::mb_add
    18

    上转型对象,书上的知识点太挫了

    package ss;
    
    class A{
    	A(){
    		System.out.println("A::构造函数");
    		show();
    	}
    	public void show(){
    		System.out.println("A:show");
    	}
    }
    class B extends A{
    	B(){
    		System.out.println("B::构造函数");
    		show();
    	}
    	public void show(){
    		System.out.println("B:show");
    	}
    }
    public class Test {
    
    	/**
    	 * @param args
    	 */
    	public static void main(String[] args) {
    		// TODO Auto-generated method stub
    		A a = new B();
    	}
    
    }
    


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  • 原文地址:https://www.cnblogs.com/lgh1992314/p/5835222.html
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