根据接口istringbuffer ,自己做一个mystringbuffer
步骤 1 : istringbuffer接口
package character; public interface istringbuffer { public void append(string str); //追加字符串 public void append(char c); //追加字符 public void insert(int pos,char b); //指定位置插入字符 public void insert(int pos,string b); //指定位置插入字符串 public void delete(int start); //从开始位置删除剩下的 public void delete(int start,int end); //从开始位置删除结束位置-1 public void reverse(); //反转 public int length(); //返回长度 }
步骤 2 : value和capacity
value:用于存放字符数组
capacity: 容量
无参构造方法: 根据容量初始化value
public mystringbuffer(){ value = new char[capacity]; } package character; public class mystringbuffer implements istringbuffer{ int capacity = 16; int length = 0; char[] value; public mystringbuffer(){ value = new char[capacity]; } @override public void append(string str) { // todo auto-generated method stub } @override public void append(char c) { // todo auto-generated method stub } @override public void insert(int pos, char b) { // todo auto-generated method stub } @override public void delete(int start) { // todo auto-generated method stub } @override public void delete(int start, int end) { // todo auto-generated method stub } @override public void reverse() { // todo auto-generated method stub } @override public int length() { // todo auto-generated method stub return 0; } }
步骤 3 : 带参构造方法
package character; public class mystringbuffer implements istringbuffer{ int capacity = 16; int length = 0; char[] value; public mystringbuffer(){ value = new char[capacity]; } //有参构造方法 public mystringbuffer(string str){ if(null!=str) value =str.tochararray(); length = value.length; if(capacity<value.length) capacity = value.length*2; } @override public void append(string str) { // todo auto-generated method stub } @override public void append(char c) { // todo auto-generated method stub } @override public void insert(int pos, char b) { } @override public void delete(int start) { // todo auto-generated method stub } @override public void delete(int start, int end) { // todo auto-generated method stub } @override public void reverse() { // todo auto-generated method stub } @override public int length() { // todo auto-generated method stub return length; } @override public void insert(int pos, string b) { } }
步骤 4 : 反转 reverse
package character; public class mystringbuffer implements istringbuffer { int capacity = 16; int length = 0; char[] value; public mystringbuffer() { value = new char[capacity]; } // 有参构造方法 public mystringbuffer(string str) { this(); if (null == str) return; if (capacity < str.length()) { capacity = value.length * 2; value = new char[capacity]; } if (capacity >= str.length()) system.arraycopy(str.tochararray(), 0, value, 0, str.length()); length = str.length(); } @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 void append(string str) { // todo auto-generated method stub } @override public void append(char c) { // todo auto-generated method stub } @override public void insert(int pos, char b) { // todo auto-generated method stub } @override public void insert(int pos, string b) { // todo auto-generated method stub } @override public void delete(int start) { // todo auto-generated method stub } @override public void delete(int start, int end) { // todo auto-generated method stub } @override public int length() { // todo auto-generated method stub return length; } public string tostring() { char[] realvalue = new char[length]; system.arraycopy(value, 0, realvalue, 0, length); return new string(realvalue); } public static void main(string[] args) { mystringbuffer sb = new mystringbuffer("there light"); sb.reverse(); system.out.println(sb); } }
步骤 5 : 插入insert 和 append
边界条件判断
插入之前,首先要判断的是一些边界条件。 比如插入位置是否合法,插入的字符串是否为空
扩容
插入字符串
修改length的值
最后修改length的值,是原来的值加上插入字符串的长度
insert(int, char)
参数是字符的insert方法,通过调用insert(int, string) 也就实现了。
append
追加,就是在最后位置插入。 所以不需要单独开发方法,直接调用insert方法,就能达到最后位置插入的效果
package character; public class mystringbuffer implements istringbuffer{ int capacity = 16; int length = 0; char[] value; public mystringbuffer(){ value = new char[capacity]; } //有参构造方法 public mystringbuffer(string str){ this(); if(null==str) return; if(capacity<str.length()){ capacity = value.length*2; value=new char[capacity]; } if(capacity>=str.length()) system.arraycopy(str.tochararray(), 0, value, 0, str.length()); length = str.length(); } @override public void append(string str) { insert(length,str); } @override public void append(char c) { append(string.valueof(c)); } @override public void insert(int pos, char b) { insert(pos,string.valueof(b)); } @override public void delete(int start) { // todo auto-generated method stub } @override public void delete(int start, int end) { // todo auto-generated method stub } @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() { // todo auto-generated method stub return length; } @override public void insert(int pos, string b) { //边界条件判断 if(pos<0) return; if(pos>length) return; if(null==b) return; //扩容 while(length+b.length()>capacity){ capacity = (int) ((length+b.length())*1.5f); 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); //把要插入的数据插入到指定位置 system.arraycopy(cs, 0, value, pos, cs.length); length = length+cs.length; } public string tostring(){ char[] realvalue = new char[length]; system.arraycopy(value, 0, realvalue, 0, length); return new string(realvalue); } public static void main(string[] args) { mystringbuffer sb = new mystringbuffer("there light"); system.out.println(sb); sb.insert(0, "let "); system.out.println(sb); sb.insert(10, "be "); system.out.println(sb); sb.insert(0, "god say:"); system.out.println(sb); sb.append("!"); system.out.println(sb); sb.append('?'); system.out.println(sb); sb.reverse(); system.out.println(sb); } }
步骤 6 : 删除 delete
package character; public class mystringbuffer implements istringbuffer{ int capacity = 16; int length = 0; char[] value; public mystringbuffer(){ value = new char[capacity]; } //有参构造方法 public mystringbuffer(string str){ this(); if(null==str) return; if(capacity<str.length()){ capacity = value.length*2; value=new char[capacity]; } if(capacity>=str.length()) system.arraycopy(str.tochararray(), 0, value, 0, str.length()); length = str.length(); } @override public void append(string str) { insert(length,str); } @override public void append(char c) { append(string.valueof(c)); } @override public void insert(int pos, char b) { insert(pos,string.valueof(b)); } @override public void delete(int start) { delete(start,length); } @override public void delete(int start, int end) { //边界条件判断 if(start<0) return; if(start>length) return; if(end<0) return; if(end>length) return; if(start>=end) return; system.arraycopy(value, end, value, start, length- end); length-=end-start; } @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() { // todo auto-generated method stub return length; } @override public void insert(int pos, string b) { //边界条件判断 if(pos<0) return; if(pos>length) return; if(null==b) return; //扩容 while(length+b.length()>capacity){ capacity = (int) ((length+b.length())*1.5f); 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); //把要插入的数据插入到指定位置 system.arraycopy(cs, 0, value, pos, cs.length); length = length+cs.length; } public string tostring(){ char[] realvalue = new char[length]; system.arraycopy(value, 0, realvalue, 0, length); return new string(realvalue); } public static void main(string[] args) { mystringbuffer sb = new mystringbuffer("there light"); system.out.println(sb); sb.insert(0, "let "); system.out.println(sb); sb.insert(10, "be "); system.out.println(sb); sb.insert(0, "god say:"); system.out.println(sb); sb.append("!"); system.out.println(sb); sb.append('?'); system.out.println(sb); sb.reverse(); system.out.println(sb); sb.reverse(); system.out.println(sb); sb.delete(0,4); system.out.println(sb); sb.delete(4); system.out.println(sb); } }
练习:
使用java自带的 stringbuffer 和 这个我们自己开发的mystringbuffer性能比较。
参考比较方案:
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