java基础——MyStringBuffer

ゝ一纸荒年。 2023-06-27 11:10 2阅读 0赞

package string;
    
    public interface IStringBuffer { 
    	//接口
        public void append(String str);
        public void append(char c);
        public void insert(int pos,char b);
        public void insert(int pos,String b);
        public void delete(int start);
        public void delete(int start,int end);
        public void reverse();
        public int length();
    }

package string;
    
    public class MyStringBuffer implements IStringBuffer { 
    	//实现类
        int capacity = 16;//容量
        int length = 0;//长度
        char[] value;//字符数组，操作进行组
        public MyStringBuffer(){ //无参构造函数
            value  = new char[capacity];//初始化capacity大小字符数组
        }
    
        public MyStringBuffer(String str){ //有参构造函数
            this();//调用无参构造函数
            if(null == str){ 
                return;
            }
            if(capacity < str.length()){ //如字符串长度大于初始化建立的数组大小，扩容
                capacity = value.length*2;
                value = new char[capacity];
            }
            if(capacity>=str.length()){ 
                System.arraycopy(str.toCharArray(),0,value,0,str.length());//字符串转化为字符数组，复制到value数组中
            }
            length  = str.length();//长度
        }
    
        public static void main(String[] args){ 
            MyStringBuffer msb = new MyStringBuffer("abcdefghigh");
            //msb.reverse();
            System.out.println(msb);
            msb.insert(0,"aha ");
            System.out.println(msb);
            msb.insert(0,'b');
            System.out.println(msb);
    
            msb.append('c');
            System.out.println(msb);
            msb.append(" dddd");
            System.out.println(msb);
    
            msb.delete(0,4);
            System.out.println("delete test: "+msb);
    
            msb.delete(12);
            System.out.println(msb);
    
    
        }
    
        @Override
        public void append(String str) { 
            insert(length,str);
        }
    
        @Override
        public void append(char c) { 
            insert(length,String.valueOf(c));
        }
    
        @Override
        public void insert(int pos, char b) { 
            insert(pos,String.valueOf(b));
        }
    
        @Override
        public void insert(int pos, String b) { 
            if(pos<0){ 
                return;
            }
            if(pos>length){ 
                return;
            }
            if(null==b){ 
                return;
            }
            while((length+b.length())>capacity){ 
                capacity =(int)((length+b.length()) *2f);
                char[] newValue = new char[capacity];
                System.arraycopy(value,0,newValue,0,length);
                value = newValue;
            }
    
            char[] cs = b.toCharArray();
            //先把已经存在的数据往后移
            System.arraycopy(value,pos,value,pos+cs.length,length-pos);
            //插入数据
            System.arraycopy(cs,0,value,pos,cs.length);
    
            length += cs.length;
        }
    
        @Override
        public void delete(int start) { 
            delete(start,length);
        }
    
        @Override
        public void delete(int start, int end) { 
            if(start<0){ 
                return;
            }
            if(end<0){ 
                return;
            }
            if(end<start){ 
                return;
            }
            if(end>length){ 
                return;
            }
    
            //后面的数据移过来
            System.arraycopy(value,end,value,start,length-end);
    
            length -= end-start;
    
            //System.arraycopy(value,0,value,0,length);//是否要考虑有覆盖不足情况？？
        }
    
        @Override
        public void reverse() { 
            for(int i=0;i<length/2;i++){ 
                char temp = value[i];
                value[i] = value[length-i-1];
                value[length-i-1] = temp;
            }
        }
    
        @Override
        public int length() { 
            return length;
        }
    
        public String toString(){ 
            char[] realValue = new char[length];
            System.arraycopy(value,0,realValue,0,length);
            return new String(realValue);
    
        }
    }